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Correlation and causation

How can you separate correlated changes from causal explanation?

Scientific and statistical thinking

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

The base rate of an event

Why does an event's base rate change the meaning of a positive signal?

Scientific and statistical thinking

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

Sampling error

How can you assess how sample composition affects conclusions?

Scientific and statistical thinking

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

Systematic bias

How can you identify systematic selection or measurement bias?

Scientific and statistical thinking

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

Effect size

How can you distinguish effect size from the existence of a difference?

Scientific and statistical thinking

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

Measurement uncertainty

How can you report a measurement together with its uncertainty?

Scientific and statistical thinking

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

Sources and personal interpretation

How can you separate a cited source from personal interpretation in a note?

A personal knowledge base

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

An atomic note

How can you extract one independent idea while preserving needed context?

A personal knowledge base

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

Connections between notes

How can you link notes by a meaningful relationship between ideas?

A personal knowledge base

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

An observation plan

How can you define observations discriminating between explanations?

Practical experiments and hobbies

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

A repeatable measurement

How can you repeat a measurement while recording conditions and variation?

Practical experiments and hobbies

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon

Understanding how a household object works

How can you map household-object parts to their functions?

Practical experiments and hobbies

Difficulty: Intermediate
Audience: Researcher
Audience: Curious reader
Purpose: Evaluate hypotheses and sources
Coming soon
Complete text outline
Research and evidence
Research and sources
  1. Facts, interpretations, and opinions
  2. An evidence register
  3. Finding a primary source
  4. Checking dates and context
  5. Verifying a numerical claim
  6. Reading a regulatory document
  7. Working with an uncertain conclusion
  8. A citation chain
  9. Comparing conflicting sources
  10. Correcting a published error
Scientific and statistical thinking
  1. A testable hypothesis
  2. A control group
  3. Correlation and causation
  4. The base rate of an event
  5. Sampling error
  6. Systematic bias
  7. Effect size
  8. Measurement uncertainty
  9. Reproducibility of a result
  10. Updating a belief with new evidence
A personal knowledge base
  1. A subject-area index
  2. What is worth saving in notes
  3. Sources and personal interpretation
  4. An atomic note
  5. Connections between notes
  6. Finding previously studied material
  7. Turning notes into an explanation
  8. Updating outdated information
  9. Archiving a completed project
  10. Evaluating a knowledge base through work
Practical experiments and hobbies
  1. A question for a personal experiment
  2. An observation plan
  3. A repeatable measurement
  4. Understanding how a household object works
  5. Photographic observation of one object
  6. Documenting a repair
  7. Comparing tools on the same task
  8. Learning a new manual skill
  9. A shared practical project
  10. Applying a lesson from a hobby at work
The digital platform
The anatomy of a SaaS superapp
  1. Mapping the platform: components and responsibilities
  2. Domains and module boundaries
  3. Functional requirements and architectural constraints
  4. Tracing a user request through the system
  5. Tracing an event from action to outcome
  6. Deployment topology: processes, nodes, and regions
  7. Mapping dependencies and failure domains
  8. A modular monolith and conditions for extracting services
  9. Evolving architecture as a product grows
  10. Reviewing architectural decisions for consistency
SaaS domain modeling
  1. Users, organizations, and memberships
  2. Workspaces and nested spaces
  3. Inviting a member
  4. Tenant data isolation
  5. Shared databases and database-per-tenant
  6. Tenant provisioning
  7. Transferring organization ownership
  8. Organization quotas
  9. Exporting customer data
  10. Deleting a tenant and related resources
Subscriptions and payments
  1. Products, prices, plans, and subscriptions
  2. Entitlements and capability checks
  3. Trials and conversion to a paid plan
  4. Metered billing
  5. Payment webhooks and redelivery
  6. Reconciling internal state with a provider
  7. Proration when changing a plan
  8. Failed payments and dunning
  9. Refunds and billing adjustments
  10. Migrating plans for existing customers
Superapp modules
  1. Projects, tasks, and configurable statuses
  2. Comments, mentions, and discussions
  3. Notifications and user preferences
  4. Files and sharing
  5. Custom fields
  6. Full-text search across a product
  7. Event-driven automations
  8. Webhooks for external integrations
  9. SDKs and extension contracts
  10. Plugin permissions and isolation
Platform frontend
  1. Application shells and product modules
  2. Routing and nested screens
  3. Server state and client state
  4. Optimistic updates and rollback
  5. Handling API errors in the interface
  6. Accessibility for complex forms
  7. Interface localization and plural forms
  8. Offline operations and synchronization
  9. Performance of a large interface
  10. Dates, currencies, and time zones
Application APIs and protocols
  1. Designing REST API resources
  2. HTTP methods, status codes, and error semantics
  3. Idempotent HTTP operations
  4. OpenAPI and contract validation
  5. gRPC and protobuf compatibility
  6. GraphQL schemas and query cost
  7. SSE and WebSocket for interface updates
  8. Cursor pagination
  9. GraphQL federation and schema boundaries
  10. Versioning a public API
Browser sessions, cookies, and CSRF
  1. Authentication, authorization, and sessions: separate responsibilities
  2. The sign-in journey: browser, provider, session and API
  3. The lifecycle of a server-side session
  4. Cookie attributes: Domain, Path, Secure, and HttpOnly
  5. SameSite and the boundaries of sites and origins
  6. How automatically sent credentials enable CSRF
  7. CORS, CSRF, and XSS: different threat models
  8. Implementing CSRF protection with a synchronizer token
  9. Double-submit cookies and token binding
  10. Keeping credentials out of browser JavaScript with a BFF
  11. Checking Origin, Referer, and Fetch Metadata
JWT
  1. Inside a JWT: header, payload, and signature
  2. Choosing between JWTs and opaque tokens
  3. Symmetric and asymmetric token signatures
  4. Access and refresh tokens: different lifetimes
  5. JWTs between services and trust boundaries
  6. Validating issuer, audience, expiration, and time
  7. Algorithm selection and signature validation failures
  8. JWKS, key caching, and rotation
  9. Refresh token rotation and reuse detection
  10. Revoking JWT access before expiration
OAuth, OIDC, and external identity providers
  1. OAuth participants and delegated access
  2. The authorization code flow with PKCE
  3. ID tokens and access tokens in OIDC
  4. Discovery metadata and OIDC client configuration
  5. Integrating Google sign-in
  6. Integrating GitHub login and retrieving a profile
  7. Integrating Microsoft Entra ID
  8. Integrating Sign in with Apple
  9. The distinct purposes of state, nonce, and PKCE
  10. Linking an external account to an existing user
Permissions and Ory Keto
  1. RBAC: roles and permissions
  2. ABAC: attribute-based policies
  3. ReBAC: permissions through object relationships
  4. Access inheritance in organizations and projects
  5. Modeling relationships for documents and folders
  6. Representing relationships in Ory Keto
  7. Checking permissions in an application API
  8. Relationship changes and access consistency
  9. Testing a permission matrix
  10. Permission check performance and safe caching
Ory Oathkeeper and policy enforcement
  1. Policy enforcement at the application boundary
  2. When authorization belongs inside a business operation
  3. Reverse proxy and decision API integration
  4. Route rules and request matching
  5. Authenticating incoming requests
  6. Passing identity context to an application
  7. Integrating permission checks with Keto
  8. Trusted headers and spoofing prevention
  9. Handling failures and unavailable dependencies
  10. Integration tests for access policies
Account lifecycle and stronger authentication
  1. Password storage and hashing parameters
  2. Email verification without account takeover
  3. Account recovery and trust boundaries
  4. Enrolling and verifying a TOTP second factor
  5. WebAuthn and passkeys
  6. Step-up authentication for sensitive actions
  7. Managing active devices and sessions
  8. Recovery codes and MFA recovery
  9. Suspension, deletion, and account re-registration
  10. Migrating between identity systems
Ory Kratos
  1. Where Kratos fits in an identity system
  2. Designing identity schemas and traits
  3. Browser flows and API flows
  4. Registration and contact verification
  5. Signing in and obtaining a session
  6. Building a custom interface for self-service flows
  7. Connecting an external OIDC provider
  8. Account recovery and profile updates
  9. Migrating users to Kratos
  10. Operating Kratos: configuration, upgrades, and diagnosis
Ory Hydra
  1. Hydra's responsibilities in an OAuth/OIDC architecture
  2. Client registration and redirect URI management
  3. Connecting Hydra to a separate login system
  4. Login challenges and consent challenges
  5. Implementing the authorization code flow in an application
  6. Client credentials for service-to-service access
  7. Scopes, audiences, and claims
  8. Introspection, revocation, and ending access
  9. Signing keys and their rotation
  10. Diagnosing OAuth flow failures
Keycloak
  1. Mapping realms, clients, and users
  2. Connecting an application through OIDC
  3. Client roles, realm roles, and groups
  4. Protocol mappers and token contents
  5. Identity brokering with an external provider
  6. Federation with LDAP and corporate directories
  7. Configuring authentication flows
  8. Sessions, SSO, and logout
  9. Extending and styling user flows
  10. Operations: clustering, upgrades, backups, and auditing
Specialized storage systems
  1. Choosing storage by query and recovery requirements
  2. S3 objects, keys, and metadata
  3. Document databases and aggregate modeling
  4. Measuring column-oriented storage on an example
  5. A search index as derived data
  6. SQLite for products and local tools
  7. Presigned URLs and limited access
  8. ClickHouse for event analytics
  9. Vector storage and result filtering
  10. Multipart uploads for large files
PostgreSQL data modeling and integrity
  1. Platform data: sources of truth, indexes and copies
  2. Choosing data types
  3. Primary keys and record identity
  4. Foreign keys and entity relationships
  5. Unique and check constraints
  6. Normalization and deliberate denormalization
  7. A transaction for a business operation
  8. Isolation levels under conflicting requests
  9. Row locks and deadlocks
  10. Advisory locks
  11. Schema migrations without application downtime
PostgreSQL queries and performance
  1. B-tree indexes
  2. EXPLAIN and EXPLAIN ANALYZE
  3. GIN and searching compound data
  4. Window functions
  5. Partitioning large tables
  6. Composite indexes and column order
  7. Partial and expression indexes
  8. N+1 queries and batch loading
  9. Autovacuum and dead tuple accumulation
  10. Connection pooling and concurrency limits
Operating PostgreSQL
  1. WAL and state recovery
  2. Physical replication
  3. Logical replication
  4. Replica lag and stale reads
  5. Backups and point-in-time recovery
  6. Failover and fencing
  7. Major version upgrades
  8. Monitoring locks and long transactions
  9. Disk capacity planning
  10. Database recovery exercises
Redis data models and commands
  1. Redis in the platform: fast data and responsibility boundaries
  2. A cached request: reads, misses, updates and staleness
  3. Choosing a Redis data structure for a task
  4. Strings and atomic operations
  5. Hashes for object data
  6. Sets and set operations
  7. Sorted sets and ordered queries
  8. TTL and the lifecycle of a key
  9. Pipelining to reduce network exchanges
  10. MULTI/EXEC and optimistic locking
  11. Lua and server-side functions for compound operations
  12. Memory and eviction policies
Redis application patterns
  1. Cache-aside in an API
  2. Write-through and write-behind caching
  3. Invalidating a cache after data changes
  4. Rate limiting with Redis
  5. A leaderboard with score updates
  6. Pub/Sub for transient notifications
  7. Redis Streams for persistent event streams
  8. Cache stampedes and coordinated key refreshes
  9. Hot keys and distributing requests
  10. Distributed locks and their limitations
Operating Redis
  1. RDB and snapshot recovery
  2. AOF and write durability
  3. Replication and replica lag
  4. Redis Cluster and slot distribution
  5. ACLs, TLS, and access boundaries
  6. Sentinel and primary failover
  7. Resharding a running system
  8. Diagnosing latency and slow commands
  9. Verifying backups through recovery
  10. Upgrading Redis and verifying application behavior
Distributed systems patterns
  1. Consistency models in user scenarios
  2. CAP and its scope of applicability
  3. CQRS and separate read models
  4. Event sourcing and state reconstruction
  5. Leader election
  6. Leases and time-limited ownership
  7. Distributed locks and fencing tokens
  8. Saga choreography and orchestration
  9. An anti-corruption layer for an external system
  10. Strangler migration of a running product
Messaging architecture
  1. Commands, events, and messages: different intentions
  2. A message in the system: producer, broker and consumer
  3. At-most-once and at-least-once in one scenario
  4. The transactional outbox pattern
  5. Inbox and processing deduplication
  6. Partition keys and processing order
  7. Backpressure between producer and consumer
  8. When a PostgreSQL-backed queue is sufficient
  9. Kafka, NATS, and RabbitMQ in a controlled comparison
  10. The boundaries of exactly-once guarantees
  11. Event versioning
Temporal: durable execution fundamentals
  1. The problem durable execution solves
  2. Separating Workflow and Activity code
  3. Event history and execution recovery
  4. Determinism and Workflow code constraints
  5. Workflow failures and Activity failures
  6. Process results and process state
  7. The boundary between Temporal and the application database
  8. Workers and task queues
  9. A long-running business process worked example
  10. Idempotent external actions in Activities
Temporal process mechanisms
  1. Signals for external events
  2. Queries for reading state
  3. Updates for controlled process changes
  4. Child Workflows and process decomposition
  5. Schedules and periodic execution
  6. Sagas and compensation in a Workflow
  7. Retry policies for different failures
  8. Activity timeouts and their interactions
  9. Heartbeats and long-running operations
  10. Cancellation and orderly termination
Changing and operating Temporal workflows
  1. Workflow and Activity observability
  2. Self-hosted and managed Temporal against explicit requirements
  3. Unit testing a Workflow with controlled time
  4. Checking compatibility through replay
  5. Changing Workflow code with patching
  6. Worker Versioning and worker deployment
  7. Continue-As-New and history growth
  8. Scaling workers for the workload
  9. History retention and archival
  10. Recovering from an external integration failure
Core NATS
  1. Pub/Sub and subjects in Core NATS
  2. Subject hierarchies and wildcard subscriptions
  3. Request/reply over NATS
  4. Queue groups and work distribution
  5. Accounts, credentials, and subject permissions
  6. Subscriber behavior during a disconnection
  7. Slow consumers and buffer limits
  8. Reconnecting and restoring subscriptions
  9. Draining and graceful application shutdown
  10. Clusters, gateways, and leaf nodes
NATS JetStream
  1. Streams and consumers as separate entities
  2. Message retention policies
  3. Pull consumers and push consumers
  4. Durable consumers and resuming consumption
  5. Acknowledgments and redelivery
  6. Publication deduplication and its limits
  7. Replay and history reprocessing
  8. Stream replication and node failure
  9. Storage limits and load management
  10. Diagnosing consumer lag and state
RabbitMQ queues and routing
  1. Producers, exchanges, queues, and consumers
  2. Direct exchanges and exact routing
  3. Topic exchanges and routing key patterns
  4. Fanout exchanges for broadcast
  5. Bindings and topology design
  6. Connections, channels, and their lifecycle
  7. Durable queues and persistent messages: different properties
  8. Consumer acknowledgments
  9. Prefetch and in-flight message counts
  10. Publisher confirms
Reliable processing with RabbitMQ
  1. Quorum queues and their replication model
  2. Redelivery and consumer idempotency
  3. Dead-letter exchanges and failure review queues
  4. TTL and delayed retries
  5. Poison messages and endless processing loops
  6. Message ordering with multiple consumers
  7. Graceful consumer shutdown
  8. Connection loss during publication
  9. Flow control during broker overload
  10. Topology migration without losing messages
RabbitMQ streams and operations
  1. Streams as replayable logs
  2. Choosing between a queue and a stream
  3. Users, virtual hosts, and permissions
  4. Offsets and resuming reads after failure
  5. Stream retention by time and size
  6. Superstreams and partition distribution
  7. Queue, connection, and consumer metrics
  8. Disk and memory alarms
  9. Clustering and node failures
  10. Upgrading and testing broker recovery
Metrics and distributed tracing
  1. A dashboard connecting metrics, logs, and traces
  2. Counters, gauges, and histograms
  3. Choosing signals with RED and USE
  4. Prometheus scraping and service discovery
  5. Instrumenting an application with OpenTelemetry
  6. Propagating trace context between services
  7. Labels and metric cardinality
  8. Histogram quantiles and interpretation errors
  9. Tracing across a message queue
  10. Sampling distributed traces
Application logging
  1. Platform observability: from user outcome to signal
  2. Structured logs and their schema
  3. Choosing log levels
  4. Request IDs, correlation IDs, and trace IDs
  5. Errors, stack traces, and useful diagnostic messages
  6. Audit logs and product event logs
  7. Logging background jobs
  8. Request context in asynchronous code
  9. Redacting secrets and personal data
  10. Sampling and limiting log volume
  11. Evaluating logs through an incident investigation
Elasticsearch for logs
  1. Documents, indices, and mappings
  2. Shards and replicas
  3. Data streams for time-based data
  4. Searching logs by structured fields
  5. Field types and dynamic mapping failures
  6. Aggregations for event analysis
  7. Lifecycle management and retention
  8. Managing high cardinality
  9. Diagnosing slow indexing
  10. Restoring indices from snapshots
Log collection and processing
  1. The ELK pipeline from application to search
  2. Logstash inputs, filters, and outputs
  3. Parsing JSON and unstructured messages
  4. Elastic Agent and collector management
  5. Fluent Bit for container log collection
  6. OpenTelemetry Collector in a telemetry pipeline
  7. Enriching events with infrastructure metadata
  8. Comparing Elastic, OpenSearch, and Loki for a workload
  9. Multiline events and stack traces
  10. Buffering when storage is unavailable
Computing environment fundamentals
  1. Processes and virtual memory
  2. Threads and execution scheduling
  3. Stack and heap
  4. Garbage collection
  5. System calls and the user/kernel boundary
  6. Filesystems and input/output operations
  7. TCP connections and retransmission
  8. Event loops and asynchronous input/output
  9. Compilation, interpretation, and runtimes
  10. Numbers, encodings, time, and representation errors
DNS and domain names
  1. Recursive and authoritative DNS
  2. A, AAAA, CNAME, and other records
  3. Delegation and zone management
  4. TTL and change propagation
  5. Split-horizon DNS
  6. DNSSEC and the chain of trust
  7. DNS over HTTPS and DNS over TLS
  8. Negative caching
  9. Moving a domain between hosting locations
  10. Diagnosing inconsistent DNS answers
IPAM and address space
  1. Planning infrastructure addressing
  2. CIDR and subnet calculation
  3. Public and private address ranges
  4. IPv6 prefix planning
  5. VLANs and their relationship to addressing
  6. VRFs and overlapping address spaces
  7. Tracking prefixes and addresses in NetBox
  8. IPAM as a data source for automation
  9. Detecting address conflicts and orphaned allocations
  10. Migrating address space
Service discovery and Consul
  1. Service registries and DNS: separate responsibilities
  2. Registering a service instance
  3. Health checks and removing unavailable instances
  4. Client-side and server-side discovery
  5. The DNS interface to service discovery
  6. The Consul catalog HTTP API
  7. Consul and Kubernetes discovery in the same scenario
  8. TTL and stale registration detection
  9. Caching discovery results
  10. Registry failure and running-system behavior
Docker: how containers work
  1. The delivery system: from source code to a running version
  2. Images, containers, and processes
  3. Linux namespaces
  4. Cgroups and resource limits
  5. Image layers and copy-on-write
  6. Exit codes and container lifecycle
  7. Volumes and data persistence
  8. Container networking
  9. Rootless containers
  10. PID 1 and signal handling
  11. Diagnosing a container that exits immediately
OCI and image registries
  1. Registries, repositories, tags, and digests
  2. Manifests, image indices, and blobs
  3. What happens during push and pull
  4. Authenticating a registry client
  5. Deploying an OCI registry
  6. Harbor projects and access control
  7. Mirrors and caching external images
  8. Immutable tags and image promotion
  9. Registry retention and garbage collection
  10. Signatures, provenance, and verification before execution
Docker builds and local environments
  1. Dockerfiles and build-step caching
  2. Multi-stage builds
  3. BuildKit and build context management
  4. Multi-platform images
  5. Choosing a base image
  6. Docker Compose for an integration environment
  7. Passing secrets during builds
  8. Reproducible application builds
  9. Health checks and dependency readiness
  10. Optimizing image size and build time
Kubernetes core objects
  1. Control planes and worker nodes
  2. The API server and declarative state
  3. Pods and their containers
  4. Deployments and ReplicaSets
  5. StatefulSets and instance identity
  6. DaemonSets for per-node workloads
  7. Jobs and CronJobs
  8. Labels, selectors, and namespaces
  9. Requests, limits, and QoS
  10. Readiness, liveness, and startup probes
Kubernetes networking
  1. The Pod-to-Pod network model
  2. ClusterIP Services
  3. CNI and address allocation
  4. Headless Services
  5. DNS for Services and Pods
  6. Ingress and the Gateway API
  7. NetworkPolicy
  8. Balancing external traffic
  9. EndpointSlices and backend selection
  10. Diagnosing network failures between Pods
Kubernetes storage
  1. Volumes and the Pod lifecycle
  2. PersistentVolumes and PersistentVolumeClaims
  3. StorageClasses and dynamic provisioning
  4. CSI and storage integration
  5. StatefulSets and data persistence
  6. Volume snapshots
  7. Access modes and shared-access constraints
  8. Expanding a volume
  9. Backing up an application and its data
  10. Moving stateful workloads between clusters
Kubernetes access and isolation
  1. ServiceAccounts and workload identity
  2. Kubernetes RBAC
  3. Pod Security Standards
  4. Application access to the Kubernetes API
  5. Workload identity for external services
  6. Secrets and their delivery to Pods
  7. Admission policies
  8. SecurityContexts and Linux capabilities
  9. Multi-tenancy and namespace boundaries
  10. Auditing Kubernetes API activity
Operating Kubernetes
  1. Scheduling, affinity, and anti-affinity
  2. Taints and tolerations
  3. Operators and reconciliation loops
  4. PodDisruptionBudgets
  5. HPA and scaling metric selection
  6. Scaling nodes
  7. Upgrading a cluster
  8. Draining and maintaining a node
  9. Diagnosing Pending, CrashLoopBackOff, and OOMKilled
  10. Recovering the control plane and critical components
Testing and CI
  1. CI pipelines and verifiable release gates
  2. The boundaries of a unit test
  3. Integration tests with real dependencies
  4. Contract tests for an external API
  5. An end-to-end user scenario
  6. Property-based testing
  7. Managing fixtures and test data
  8. Fuzz testing inputs
  9. Race detection
  10. Flaky tests and finding their cause
Infrastructure as Code and GitOps
  1. Declarative infrastructure configuration
  2. Terraform state and change locking
  3. Terraform modules
  4. Ansible and idempotent node configuration
  5. Helm and application configuration
  6. Kustomize and environment differences
  7. Argo CD and reconciliation
  8. Plan reviews and drift detection
  9. Promoting changes between environments
  10. Rolling back an infrastructure change
PKI, secrets, and the software supply chain
  1. Trust boundaries: a platform-wide protection map
  2. Certificates, keys, and trust chains
  3. Running a certificate authority
  4. ACME and automated certificate renewal
  5. mTLS between services
  6. OpenBao and issuing application secrets
  7. Dynamic credentials
  8. External Secrets and Kubernetes synchronization
  9. SBOMs and dependency provenance
  10. Rotating a secret without stopping its consumer
  11. Verifying signed artifacts in a delivery pipeline
  12. A backdoored coding assignment: safely reviewing an untrusted repository
Load testing
  1. Deriving a workload from user actions
  2. Arrival rate and concurrent user counts
  3. Open and closed workload models
  4. Throughput, latency, and errors
  5. Preparing realistic test data
  6. Warm-up and steady state
  7. Soak testing and accumulating problems
  8. Stress testing and the saturation point
  9. Coordinated omission in measurements
  10. A reproducible comparison of two solutions
Profiling and optimization
  1. Application CPU profiling
  2. Profiling Go with pprof
  3. Heap profiling and retained memory
  4. Allocations and garbage collector pressure
  5. Lock contention
  6. Network latency and round-trip counts
  7. Event loop lag in Node.js
  8. Benchmarks and statistical stability
  9. Optimizing a request's critical path
  10. Checking performance improvements for regressions elsewhere
SRE and reliability
  1. SLIs and SLOs for user outcomes
  2. Organizing incident response
  3. Error budgets and release decisions
  4. Symptom-based alerts
  5. RPO and RTO
  6. A runbook for a specific failure
  7. Postmortems with verifiable follow-up actions
  8. Burn-rate alerts
  9. Disaster recovery exercises
  10. The cost of additional reliability
Algorithms and data structures
  1. Measuring asymptotic complexity
  2. Hash tables and collision handling
  3. Heaps and priority queues
  4. Search trees
  5. Graphs and traversals
  6. Choosing a data structure by operation profile
  7. Dynamic programming
  8. Bloom filters
  9. Consistent hashing
  10. Topological sorting
Optimization, recommendations, and composition
  1. Formalizing a problem through constraints
  2. A greedy solution and a counterexample
  3. Candidates, ranking, and reranking
  4. Branch-and-bound
  5. CP-SAT for an applied problem
  6. A shared contract for multiple solvers
  7. A slot tree for a heterogeneous feed
  8. Checking optimality and feasibility
  9. Quotas, deduplication, and anti-fatigue
  10. Evaluating results against business constraints
RAG and document processing
  1. The complete RAG pipeline
  2. Chunking and semantic boundaries
  3. Embeddings and representation choice
  4. Linking evidence in an answer
  5. Extracting text from different formats
  6. Hybrid search
  7. Reranking retrieved passages
  8. Metadata filters and document permissions
  9. Updating and removing indexed documents
  10. A retrieval evaluation suite
Agent systems
  1. A model call, a workflow, and an agent
  2. An agent tool contract
  3. Authority boundaries
  4. Memory and the freshness of stored information
  5. Planning and task decomposition
  6. The Agentic OS run queue and constraints
  7. Human-in-the-loop workflows
  8. Controlling token and resource consumption
  9. Coordinating multiple agents
  10. Resuming a task after failure
AI quality and operations
  1. Datasets for evaluating an AI feature
  2. Labeling correct outcomes
  3. Regression evaluations
  4. Comparing models on your own tasks
  5. Observability for AI requests
  6. Evaluating unsupported claims
  7. Prompt injection through external content
  8. Isolating untrusted instructions
  9. Caching and inference costs
  10. Investigating a failed AI decision
A news bot and source ingestion
  1. A source registry and source properties
  2. RSS and Atom ingestion
  3. Ingestion through an official API
  4. Accepting a user-submitted link
  5. Extracting the main text of a page
  6. Topic classification and catalog linking
  7. Building a digest with verifiable links
  8. URL normalization and exact duplicates
  9. Clustering publications about one event
  10. Monitoring source failures and selection quality
Drones and the flight environment
Drone components and physics
  1. Components of an unmanned aircraft system
  2. Multirotors, fixed-wing aircraft, and VTOL
  3. Flight controllers
  4. Forces acting on an aircraft
  5. Motors and electronic speed controllers
  6. IMUs and attitude estimation
  7. GNSS and positioning
  8. A flight energy budget
  9. Thrust and propeller selection
  10. Payload and balance
Drone flight rules in Kazakhstan
  1. Bought a drone: a map of required actions
  2. The category of a specific operation
  3. Accounting and state registration
  4. Technical admission of an aircraft
  5. Operator qualifications
  6. Airspace classes
  7. Checking whether a regulatory requirement is current
  8. Permanent and temporary restrictions
  9. Flights near built-up areas
  10. Self-built aircraft and their limitations
Owner documentation and procedures
  1. Aircraft and flight logbooks
  2. Documenting aircraft provenance
  3. Preparing information for accounting
  4. Technical conformity declarations
  5. Checking supporting documents
  6. Preparing an airspace use application
  7. Coordination instructions
  8. A pilot document pack for a specific flight
  9. Coordinates, altitude, and time in documents
  10. Updating records after aircraft changes
Learning to pilot a drone
  1. A training program for a beginner pilot
  2. The observer's role
  3. Reviewing course content
  4. Choosing a training center
  5. First simulator exercises
  6. Takeoff, hovering, and landing
  7. Flying a planned path
  8. Loss-of-orientation scenarios
  9. Debriefing a training flight
  10. Readiness criteria for independent practice
Flight sites and weather
  1. Surveying a proposed flight site
  2. Obstacles and space margins
  3. People, vehicles, and changing conditions
  4. Wind at ground level and aloft
  5. Visibility and lighting
  6. Temperature and battery condition
  7. Precipitation and equipment limitations
  8. Choosing a time for a training session
  9. Gusts and terrain effects
  10. Deciding to cancel a flight
Maintenance and batteries
  1. Preflight mechanical inspection
  2. Inspecting propellers
  3. Checking motors
  4. Calibration and when it is needed
  5. Charging batteries
  6. Storing and transporting batteries
  7. Connectors, cables, and contacts
  8. Updating firmware and verifying the result
  9. Tracking cycles and signs of degradation
  10. Assessing damage after an incident
FPV and radio communication
  1. The architecture of an FPV system
  2. Radio transmitters and control receivers
  3. Analog and digital video
  4. Antennas and radiation patterns
  5. Polarization and antenna placement
  6. Checking radio-frequency requirements
  7. Radio link budgets
  8. Interference and shared spectrum
  9. Failsafe behavior after control-link loss
  10. Ground testing a completed aircraft
Traveling with a drone
  1. Checking requirements before buying tickets
  2. Finding official requirements for a new destination
  3. Airline battery rules
  4. Packing the aircraft and batteries
  5. Temporary export and reimport
  6. Preparing for a trip to the EU
  7. Preparing for a trip to the United States
  8. Preparing for a trip to Japan
  9. Preparing for a trip to Thailand
  10. A drone in Russia: registration and checking restrictions for a specific flight
  11. Transit through a third country
Aerial filmmaking
  1. Developing a short story concept
  2. Preparing a shot list before departure
  3. Camera movement and the meaning of a shot
  4. Composition from above
  5. Light and shooting time
  6. Exposure for moving images
  7. Organizing and backing up footage
  8. Editing a short aerial film
  9. Shot continuity for editing
  10. Reviewing a finished film
Applied drone missions
  1. Drone-in-a-Box as an operational system
  2. Delivering a verifiable result to a client
  3. Photogrammetry from a set of images
  4. Image overlap and flight planning
  5. Ground control points
  6. Inspecting a building
  7. Monitoring changes to an object
  8. Automated mission execution
  9. Checking model accuracy
  10. Thermal imaging and interpretation limits
Learning and skill transfer
Course design
  1. Audience and starting level
  2. The learner's final project
  3. A course skills map
  4. Prerequisite requirements
  5. Module sequencing
  6. Balancing explanation and practice
  7. Required and supplementary materials
  8. Estimating completion time
  9. Piloting the course
  10. Revising the program based on outcomes
Exercises and assessment
  1. A learning outcome expressed as an observable action
  2. A recall task
  3. An application task
  4. A transfer task for a new situation
  5. A rubric for assessing the result
  6. A practical task with multiple solutions
  7. Formative feedback
  8. Learner self-assessment
  9. Peer review of learner work
  10. Evaluating the quality of an assignment
Mentoring practice
  1. Mentoring goals and agreements
  2. Diagnosing a learner's difficulties
  3. Separating mistakes from judgments about a person
  4. Observing learner independence
  5. Questions before premature hints
  6. Calibrating the amount of help
  7. Transferring responsibility to the learner
  8. Supporting learners through repeated mistakes
  9. Concluding a mentoring relationship
  10. Reviewing mentoring program outcomes
Explaining complex ideas
  1. Identifying prior knowledge
  2. Selecting one central idea
  3. Explaining through a concrete example
  4. Analogies and their limits
  5. Moving from an example to a general principle
  6. Explaining through a counterexample
  7. Revealing a diagram step by step
  8. Checking understanding through teach-back
  9. Examining a common misconception
  10. Adapting an explanation for another audience
Onboarding a beginner at work
  1. Planning the first week
  2. Mapping the product and team
  3. A first reading of the codebase
  4. Preparing a working environment
  5. A first small change
  6. A first pull request
  7. Code review as a teaching practice
  8. A first bug investigation
  9. A first independent task
  10. Checking onboarding completion
Learning platforms
  1. Requirements for a course platform
  2. An LMS and learning progression
  3. Tracking assignments and feedback
  4. A static site for learning materials
  5. Moodle in a specific learning scenario
  6. Open edX in a specific learning scenario
  7. External platforms and dependence on their rules
  8. Accessibility of a learning environment
  9. Learning analytics and their limits
  10. Exporting and moving course materials
Live teaching
  1. Preparing a practical session
  2. Assessing a group's starting point
  3. Demonstrating while thinking aloud
  4. Solving a problem together
  5. Pair work
  6. An end-of-session assessment
  7. Supporting different learning paces
  8. Discussing group mistakes
  9. Managing questions and time
  10. Reviewing a recording of your teaching
Self-directed learning
  1. Setting a learning goal
  2. Choosing a first learning resource
  3. Planning a study week
  4. Retrieval practice
  5. Spaced repetition
  6. Interleaving task types
  7. A practical consolidation project
  8. Checking knowledge transfer
  9. Working through a learning plateau
  10. Closing a learning cycle and revising the goal
English in professional practice
  1. Reading documentation for a work task
  2. A vocabulary notebook with usage context
  3. Describing a bug in English
  4. Writing a question to a colleague
  5. Explaining an architectural decision in English
  6. Demonstrating a product in English
  7. Writing an article in English
  8. Participating in a technical discussion
  9. Working with editorial feedback
  10. Measuring progress with a repeatable task
Learning Chinese and intercultural practice
  1. Setting a goal for learning Chinese
  2. Organizing pronunciation practice
  3. Connecting pronunciation, meaning, and characters
  4. Practicing tones
  5. A personal set of flashcards
  6. Reading a short text at your level
  7. Vocabulary for a selected situation
  8. Preparing a conversation with a teacher
  9. A journal of difficulties and progress
  10. Separating cultural observation from generalization
Visual learning materials
  1. Choosing between a diagram and a table
  2. A process diagram
  3. A device cutaway
  4. Comparing two states
  5. Visualizing thresholds and ranges
  6. A five-frame explanation
  7. Coordinating text and visuals
  8. Animating a state change
  9. An interactive experiment
  10. Testing an illustration's learning value
Teams, decisions, and products
Moving into leadership
  1. The responsibilities of a senior, lead, and manager
  2. The first month in a new role
  3. Mapping stakeholder expectations
  4. Dividing time between coding and leadership
  5. Identifying team constraints
  6. Personal measures of leadership work
  7. Handing over previous technical responsibilities
  8. Making initial changes while preserving context
  9. Feedback on leadership style
  10. Reviewing the first three months
Product decisions and economics
  1. The user's problem and the proposed feature
  2. Choosing the minimum useful outcome
  3. Testing a hypothesis before development
  4. Prioritizing by expected value
  5. Total cost of ownership
  6. Feature usage metrics
  7. Build versus buy
  8. The product cost of a technical constraint
  9. Deciding to stop development
  10. Reviewing the outcome after release
Decision-making
  1. Deciding with incomplete information
  2. Decision reversibility
  3. Criteria for comparing options
  4. Explicit assumptions
  5. Distinguishing risk from uncertainty
  6. Stakeholder disagreement
  7. Documenting the reasons for a choice
  8. Conditions for reconsideration
  9. Testing decision sensitivity
  10. Reviewing a mistaken decision in hindsight
Delegation and team organization
  1. Describing the expected result
  2. Ownership of product components
  3. Choosing a task to delegate
  4. Delegating authority
  5. Boundaries for independent decisions
  6. Bus factor and knowledge distribution
  7. Intermediate checkpoints
  8. Oversight without constant intervention
  9. Redistributing overloaded work
  10. Revising the responsibility structure
Planning and delivery
  1. Breaking an outcome into stages
  2. Estimating with ranges
  3. Assumptions in time estimates
  4. Dependencies between tasks
  5. Limiting work in progress
  6. Managing unplanned work
  7. Revising plans as information changes
  8. Checking release readiness
  9. A work-cycle retrospective
  10. Analyzing recurring delays
Hiring and team development
  1. Defining the expected outcome of a role
  2. A competency matrix
  3. Consistent candidate evaluation criteria
  4. Interview questions based on real tasks
  5. A bounded practical assignment
  6. A specialist's development plan
  7. Preparing for the next level of responsibility
  8. Sharing experience within a team
  9. Comparing interviewers' observations
  10. Evaluating team learning outcomes
Feedback and conflict
  1. Preparing a conversation about a problem
  2. Observing and interpreting behavior
  3. Feedback on a specific episode
  4. Receiving feedback from a colleague
  5. Disagreement over a technical decision
  6. Conflicting priorities
  7. A broken agreement
  8. A conversation after a serious mistake
  9. Checking follow-through on new agreements
  10. Restoring a working relationship
Communication at work
  1. A concise problem statement
  2. Explaining a technical issue to business stakeholders
  3. A proposal with multiple options
  4. An architecture decision record
  5. Asynchronous discussion
  6. A meeting with a concrete outcome
  7. Demonstrating completed work
  8. A responsibility handover document
  9. Communicating during an incident
  10. A public analysis of a professional case
Wider context and visual language
Visual design
  1. Visual hierarchy
  2. Typography for long-form reading
  3. Grids and alignment
  4. Color and semantic emphasis
  5. Icons and labels
  6. Contrast and accessibility
  7. A visual language for a series
  8. Designing a printable reference card
  9. Line length and reading rhythm
  10. Testing a layout with real content
The history of technologies and standards
  1. The history of measurement units
  2. Standardizing time
  3. How a technical standard emerges
  4. The history of mass production
  5. Competing formats
  6. Compatibility with a legacy system
  7. The history of a computing interface
  8. A profession before and after technological change
  9. Infrastructure path dependence
  10. A historical case of failed adoption
Economics and supply chains
  1. A product's journey from raw material to buyer
  2. Inventory and storage costs
  3. Causes of shortages
  4. A production-chain bottleneck
  5. The cost of transportation
  6. The components of a service's cost
  7. Network effects
  8. Economies of scale and their limits
  9. Dependence on a single supplier
  10. Analyzing a service's economic model
Cities, maps, and space
  1. A map as a model of territory
  2. A city's transport network
  3. Scale and the loss of detail
  4. Map projections
  5. Distance and accessibility
  6. The distribution of urban functions
  7. Transfers as part of a route
  8. Tracing territorial change through historical maps
  9. Open geodata and its limitations
  10. Field observation of urban space
Travel and cultural observation
  1. Researching a place before traveling
  2. Planning a route under constraints
  3. Observing everyday practices
  4. Working with local sources
  5. Preparing for a language barrier
  6. Preserving context for photographs and notes
  7. Checking transport connections
  8. Reconsidering a first impression
  9. Comparing expectations with experience
  10. Preparing an informative trip report
Identity and visual design systems
  1. Brand purpose and identity boundaries
  2. From brief to touchpoint system
  3. Semantic color roles in an identity
  4. Type pairing across two languages
  5. Composition rules across touchpoints
  6. From design decisions to brand tokens
  7. A compact brand guide with worked examples
  8. Adapting identity to a product interface
  9. Checking a single brand color pair
  10. Changing a token without breaking touchpoints
Avatar creation and adaptation
  1. An avatar as a recognition tool
  2. An avatar's path from brief to profile
  3. Silhouette and small-avatar recognition
  4. References and stable visual traits
  5. Light, background, and subject separation
  6. Photography, illustration, and generated avatars
  7. An avatar set for multiple platforms
  8. Local avatar processing and export
  9. Testing a circular crop
  10. Avatar legibility at 32 pixels
Characters and visual consistency
  1. A character's role in a product
  2. From character bible to scene set
  3. A character's invariant traits
  4. Emotion through pose and expression
  5. Reference views and rotations
  6. Consistent illustrations with image references
  7. A mascot in onboarding and error messages
  8. Preparing a character for animation
  9. Detecting drift in a single character trait
  10. Transparent edges in character exports
Advertising creatives and adaptations
  1. The job of an advertising creative
  2. From offer to the post-click journey
  3. Message hierarchy in an advertisement
  4. A hook without unsupported promises
  5. Composition for placement and context
  6. Static banners and short video
  7. Adapting a creative across platforms
  8. A matrix of advertising message variants
  9. Checking one advertising text label
  10. Matching the CTA to the destination action
Visual asset production and versioning
  1. The lifecycle of a visual asset
  2. From source to publication catalog
  3. Raster, vector, and format choice
  4. Asset names, versions, and provenance
  5. Color spaces and export profiles
  6. Batch exporting sizes and formats
  7. Optimizing images for a web page
  8. A visual package manifest
  9. Checking a file's alpha channel
  10. Matching an export to its source version
Evaluating visual quality and effectiveness
  1. Criteria for visual quality
  2. From visual hypothesis to evaluation
  3. A rubric for visual variants
  4. Testing comprehension of a visual message
  5. Viewing context and evaluation limits
  6. Comparing advertising variants in an experiment
  7. Reviewing avatar and character sets
  8. From evaluation results to the next iteration
  9. One changing factor in creative comparisons
  10. Distinguishing clicks from useful outcomes
Articles and an evidence-based portfolio
A bilingual editorial practice
  1. Choosing the question an article answers
  2. Structuring an explanatory article
  3. Revising a draft
  4. A Russian-English terminology glossary
  5. Choosing a distribution channel
  6. Adapting context for the English version
  7. Independent editorial review
  8. Preparing a publication package
  9. Checking a translation for meaning
  10. Updating an article after publication
Portfolio and professional reputation
  1. A competency and evidence of its application
  2. An individual's role in a team result
  3. Explaining the limits of personal experience
  4. Connecting articles to career positioning
  5. Presenting teaching work
  6. Presenting a leadership decision
  7. A public project demonstration
  8. Anonymizing a professional case
  9. Developing a talk from an article series
  10. Evaluating the library's contribution to a portfolio

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