Tiny explainers grouped by topic. Spend less time Googling, more time building.
A battle‑tested checklist and patterns: allowlists, size limits, magic‑byte checks, streaming to object storage, virus scanning, image/PDF sanitization, signed URLs, and safe download headers.
Practical patterns for rock‑solid APIs: spec styleguide, reusable components, Problem Details errors, auth & versioning, pagination, idempotency, testing, and CI gates. Includes a copy‑paste 3.1 template.
Practical, modern defaults for CSP, HSTS, Referrer-Policy, Permissions-Policy, COOP/COEP/CORP, X-Content-Type-Options, X-Frame-Options vs frame-ancestors, cookies, and cache controls—with NGINX/Apache/Express snippets.
Commands say 'do X', events say 'X happened'. Use sagas (orchestration or choreography) for long‑running, cross‑service workflows with compensations, idempotency, and reliable messaging.
Design principles and ready-to-use patterns: consistent subcommands, great help, smart defaults, colors/TTY, progress, JSON output, config precedence, auth, errors, exit codes, and distribution.
The 80% you actually need: Pods, Deployments, Services, Ingress/Gateway, Requests/Limits, Probes, Config & Secrets, HPA, storage, and the kubectl commands you’ll use daily.
Fixed/sliding windows, token & leaky buckets, GCRA, and real-world implementations (Redis, NGINX, Envoy). Covers headers, bursts, backoff, multi‑DC, and tuning.
UTC vs local time, offsets vs zones, DST edge cases, ISO 8601/RFC 3339, DB column types, and sane patterns in JS/Python/SQL. How to store, compare, schedule, and display time without pain.
Design access + refresh flows that are safe: short-lived access tokens, rotating refresh tokens with reuse detection, device-scoped sessions, and practical revocation strategies.
Real-world settings and copy‑paste snippets for circuit breakers (closed/open/half‑open) and bulkheads (bounded concurrency/queues). Works with HTTP, gRPC, and message calls.
Pragmatic ratios, what to test where, and how to keep CI under 10 minutes: unit vs integration vs E2E, contract & component tests, data management, and flake-killers.
Freshness, validators, and directives: Cache-Control, ETag/Last-Modified, Vary, s-maxage, stale-while-revalidate, immutable. Patterns for APIs, HTML, and assets—plus CDN tips.
A practical mental model of tasks vs microtasks, when the browser renders, and patterns to keep 60fps: rAF, chunking, debouncing, and avoiding microtask traps.
Design for duplicates and reordering. Use idempotency, an inbox/outbox, and per‑key ordering to get effectively‑once processing in real systems.
Multi-stage builds, cache-friendly layering, non-root users, and sane defaults for ENTRYPOINT/CMD, healthchecks, and secrets. Copy‑paste patterns for Node, Python, and Go.
Normalization, grapheme clusters, collation, bidi, and emojis—why 'string length' and 'toLowerCase' can betray you, with practical recipes in JS/Python/SQL.
Developer token + OAuth, account hierarchy (manager vs customer), GAQL for reporting, safe mutations with validate_only/partial_failure, quotas, and offline conversions.
Use Argon2id (or bcrypt) with unique per‑user salts, optional KMS‑backed pepper, and safe on‑login migrations. Includes copy‑paste snippets for Node, Python, and Go.
Change schemas safely with backward‑compatible steps, dual writes, background backfills, and rolling deploys. Postgres‑flavored, but patterns apply to MySQL and friends.
What counts as a breaking change, URL vs header versions, deprecation signals, and how to evolve APIs without breaking clients. With routing and policy snippets you can paste today.
A practical mental model for indexes, with copy‑paste patterns for B‑tree, composite order, covering, partial, and expression indexes—plus when **not** to index.
Design request deadlines, hop timeouts, and idempotent retries with jitter so you protect upstreams, tame tail latency, and avoid cascading failures.
Low‑effort, high‑impact a11y fixes: alt text, semantic HTML & landmarks, color contrast (and non‑color cues), keyboard navigation & focus, and form labels/errors—with copy‑paste examples.
Status codes you should actually use, consistent error shapes (Problem Details, JSend), and production‑ready logging/observability—so clients get clear signals and you get actionable telemetry.
MAJOR.MINOR.PATCH — what each digit means, how pre‑releases work, and the practical rules you need for safe dependency upgrades.
A practical, skimmable template (with explanations) so your README answers the real questions: What is this? How do I run it, test it, deploy it, and debug it—today.
A gentle tour of Git’s content‑addressed storage: blobs, trees, commits, refs, and the index—so complex commands like rebase, cherry‑pick, and reset feel predictable.
A simple, diagram-first walkthrough of OAuth 2’s Authorization Code + PKCE flow—who does what (client, resource owner, authorization server, resource server), how the redirects work, and where tokens live.
DNS changes feel slow because of caching everywhere: resolvers, browsers, OSes, CDNs, and parent zones. Here’s the mental model, typical timelines, and how to plan zero‑drama cutovers.
A concise, modern walkthrough of the path from address bar to pixels: DNS lookup, HTTP/3 & TLS 1.3 handshakes, CDNs & caching, request/response, and the rendering pipeline.
A fundamental database performance problem: why N+1 happens, how to spot it, and fixes with eager loading/batching in popular ORMs (Django, Rails, Prisma/Sequelize, SQLAlchemy).
Event‑driven Nginx vs process/thread‑based Apache: performance, memory, config models, .htaccess, reverse proxying, PHP, HTTP/2/3, and how to switch without breaking prod.
Why you shouldn’t commit .env files, how to handle secrets differently in local, staging, and production, and the exact patterns to inject, validate, rotate, and audit configuration safely.
Base64 turns bytes into ASCII text for transport and storage. It is not a security mechanism. Learn how it works, common uses (MIME, URLs, JWTs), and what to use instead when you need secrecy or integrity.
As Podman’s daemonless, rootless approach gains traction, here’s a practical comparison with Docker—architecture, security, node networking/volumes, speed, and real migration paths.
A no-nonsense comparison of npm, Yarn, and pnpm: real-world differences in install speed, node_modules size, and lockfile handling—plus when to pick which.
A modern, practical comparison of Webpack and Vite: how native ESM + esbuild change dev speed, what HMR feels like, what the build story is (Rollup), and when Webpack is still the right call.
A clear, practical comparison: authN proves who you are; authZ decides what you can do. Learn identities, sessions/tokens (OIDC/OAuth2), roles/scopes/permissions, and common pitfalls.
Concurrency is about dealing with lots of things at once; parallelism is about doing lots of things at once. Here’s the mental model, practical examples, and when to use each.
A no-jargon primer on containers: how they isolate processes, how images/layers work, and what Docker/Kubernetes actually do.
A practical comparison of three ways to push updates from server to browser. Learn how each works, trade‑offs, code snippets, scaling notes, and a quick decision guide.
A practical guide to environment variables—when .env files make sense, how to load them locally, and how to keep secrets out of your repo and images.
Step-by-step: create an SSH key, add it to a server, use ssh-agent, set up ~/.ssh/config, and harden your SSH settings. Works on macOS, Linux, and Windows.
A simple walkthrough of Continuous Integration and Continuous Delivery/Deployment—what they solve, how a pipeline is structured, and a tiny example to get started.
Understand the event loop, tasks vs. microtasks, promises, and async/await; how to write concurrent code safely; and the common pitfalls (await-in-loops, timeouts, cancellation).
A whirlwind tour of widely used patterns—Singleton, Factory, Observer, Strategy, Adapter/Decorator—with tiny examples, when to use them, and common pitfalls.
Learn rebase, cherry-pick, undoing mistakes, and day-to-day flows with five commands that cover 90% of real-world Git.
A quick, practical explainer of idempotency: what it means, how HTTP methods relate, and how to implement idempotent POSTs with idempotency keys to make retries safe.
The practical trade‑offs: when a monolith (or modular monolith) is the right call, when microservices pay off, and how to evolve without pain.
A brief, practical overview of the core OOP ideas with tiny examples: how encapsulation protects invariants, when inheritance fits, and how polymorphism keeps code open to extension.
A simple guide to character encoding: what ASCII is, how UTF‑8 works, why bytes ≠ characters, and the real-world gotchas (mojibake, emojis, normalization, MySQL utf8mb4).
A fast primer on in-memory, distributed, and CDN caching—what they are, when to use each, and how they boost latency, throughput, and cost efficiency.
Demystify the TLS handshake—ClientHello, ServerHello, certificates, ECDHE key exchange, session keys—and why HTTPS protects confidentiality, integrity, and authenticity.
A high-level comparison of relational and non-relational databases with common use cases for each.
A simple explainer of API gateways—how they centralize auth, rate limiting, routing, and observability—and when to adopt one versus calling services directly.
A quick, practical guide to choosing between REST, GraphQL, and gRPC for new and existing services.
A fast primer on Cross-Origin Resource Sharing—what “origin” means, how simple vs. preflighted requests work, when to send credentials, and the exact headers that fix the dreaded CORS error.
A quick mental model to read and write cron schedules without Googling.
A handful of patterns that cover 80% of cases, with explainers.