Learn how web software really works
Free lessons on how web software really works. Predict what the code does, then see the mechanism.
- 42 courses
- 403 lessons
- Free
- No account
- Short videos
Courses
Frontend & web platform
- JavaScript runtime & language mechanicsHow JavaScript runs your code: one thread, the event loop, promises and cancellation, plus how DOM events and memory work.7 lessons
- ReactHow React actually renders, keeps state, syncs effects and handles async UI. Each lesson starts from a small program you can predict, then walks through why it behaves that way.10 lessons
- Next.js App RouterThe Next.js App Router: what runs on the server or the client, how data is fetched and cached, and which server entry points are public endpoints.6 lessons
- TypeScriptTypeScript's type system as it really works: structural typing, unknown and never, narrowing, generics, utility types, and why types vanish at runtime.6 lessons
- Browser internals & performanceHow the browser turns code into pixels, what Core Web Vitals measure, and how to ship less JavaScript.7 lessons
- Web networkingWhat happens on the wire: HTTP semantics, connections and HTTP/2 and 3, caching headers, CORS, cookies and service workers.6 lessons
- HTML, CSS & accessibilityAccessible HTML, focus and keyboard handling, WCAG 2.2, the CSS cascade and modern layout, and right-to-left interfaces.6 lessons
- Frontend system designFrontend system design with the RADIO framework: components, data, rendering, real-time, scale and security, then ten worked design prompts.25 lessons
- Angular to React translationFor Angular developers moving to React: signals vs state, change detection vs re-rendering, dependency injection vs context, and RxJS vs query caches.4 lessons
- Technical SEOHow search engines crawl, render and index JavaScript apps, and how canonicals, hreflang, sitemaps and structured data steer them.2 lessons
- JS kata bankSmall JavaScript utilities to write from scratch: debounce, throttle, Promise.all, a promise pool, retry, an event emitter, memoize, deep clone, an LRU cache and more.19 lessons
- React UI-build bankReact components to build end to end: a typeahead, a data table, infinite scroll, an uploader, accessible widgets, forms, toasts and nested comments.10 lessons
Backend, APIs, security & data
- API design & contractsDesigning HTTP APIs that hold up: method semantics, error contracts, versioning, pagination, idempotency, concurrency, rate limits, webhooks and uploads.12 lessons
- Node.js runtime internalsNode.js internals: event loop phases, nextTick vs microtasks, the thread pool, blocking, streams, scaling, memory, graceful shutdown and module systems.9 lessons
- NestJS architectureNestJS architecture: modules and dependency injection, provider scopes, the request pipeline and validation at the boundary.4 lessons
- Authentication, identity & authorizationPasswords, MFA and passkeys, where browsers keep credentials, token rotation, OAuth with PKCE and OIDC, authorization models and tenant isolation.6 lessons
- Web & API securityWeb and API security: the OWASP map, XSS and CSP, CSRF, SQL injection, broken object-level authorization, SSRF, secrets and the supply chain.8 lessons
- Relational databases: PostgreSQL in depthPostgreSQL in depth: indexes and query plans, N+1 queries, window functions, MVCC and isolation, locking, schema design, migrations and scaling.17 lessons
- Redis & NoSQL storesRedis data structures, persistence and eviction, and how to choose between document, key-value, wide-column, graph, search and vector stores.3 lessons
- CachingWhere caches sit, cache-aside reads and writes, how caches learn of change, and what goes wrong under load.4 lessons
- Async processing & messagingBackground jobs and messaging: job lifecycles, retries and dead letters, idempotent consumers, the outbox pattern, and queues vs logs.5 lessons
Systems, architecture & delivery
- Software-engineering foundationsSoftware-engineering foundations: process models, Scrum and Kanban, requirements, estimation, Git workflows, delivery metrics and technical debt.8 lessons
- System design fundamentalsSystem design fundamentals: estimation, running a design round, stateless tiers, CDNs, consistency models, overload protection and availability.8 lessons
- System design scenario bankWorked system design scenarios: a URL shortener, notification fan-out, chat, uploads, search, an exam platform, a traffic spike, multi-tenant SaaS and ticketing.13 lessons
- Distributed-systems basicsDistributed systems basics: partial failure, retries with jitter, circuit breakers, clocks, consensus, locks with fencing tokens, sagas and CQRS.8 lessons
- Software architectureSoftware architecture: bounded contexts, monolith vs microservices, ports and adapters, monorepos, events, feature flags, the strangler fig and decision records.8 lessons
- DevOps and cloudShipping software: Docker images, CI/CD, deployment strategies, infrastructure as code and Kubernetes, cloud networking, IAM and serverless.7 lessons
- Observability and reliabilityObservability and reliability: logs, metrics and traces, percentiles, OpenTelemetry, SLOs and error budgets, incident response and postmortems.8 lessons
- Testing strategyTesting strategy: the pyramid and the trophy, test doubles, contract tests, TDD, testing React, NestJS and end to end, flaky tests and mutation testing.9 lessons
- SOLID and design patternsSOLID and design patterns in TypeScript, Node, NestJS and React, and how to tell when a pattern is over-engineering.38 lessons
- DSA-lightData structures and algorithms at medium level: Big-O of JavaScript built-ins, hash maps, stacks, heaps, two pointers, binary search, BFS/DFS and memoization.8 lessons
- Scale managementScaling systems and teams: capacity math, tail latency, load testing, autoscaling, backpressure, data scaling, cost, ownership and release management.27 lessons
- Engineering judgmentPractical engineering judgment: framing problems, trade-offs, deciding with incomplete information, changing code safely, debugging method and scoping.22 lessons
- Incident scenario bankProduction incidents to work through: 502s after a deploy, slow queries, connection spikes, cache stampedes, memory leaks, and CORS, CDN and cookie bugs.12 lessons
Interview performance & AI-era engineering skills
- The interview loop itselfHow tech interview loops work: what each round scores, hire vs level signal, the recruiter screen, salary negotiation and running several processes at once.7 lessons
- Code comprehension and MR / code reviewReading code you didn't write and reviewing merge requests: defect scans, async and security lenses, test gaps, and clear review comments.10 lessons
- Pair programmingPair-programming interviews: clarify and plan, narrate while you code, test as you go, take hints well, and extend an existing codebase.5 lessons
- Take-home executionTake-home assignments: scoping, quality signals, testing under a time-box, commit history, the README and defending your work in the review call.6 lessons
- AI-assisted coding and verificationCoding with AI assistants: the rules interviews set, common failure modes, owning every line, directing the AI and verifying what it writes.7 lessons
- Communication frameworks as trainable skillsCommunicating technical answers: answer shapes, trade-off sentences, saying "I don't know" well, pacing a design round and debugging out loud.8 lessons
- English interview deliveryTechnical English for interviews: precise mechanism vocabulary, saying numbers clearly, repairing misunderstandings, and pacing under stress.5 lessons
- Rehearsal, taper and interview dayThe final stretch before interviews: mock interviews under pressure, the last two weeks, and an interview-day routine.3 lessons