Learn engineering
221 topics across 48 cards, from first principles to the decisions senior and staff interviews actually probe. 96 of them are advanced. Every topic says why a choice was made rather than only what it was, and every number carries the source it came from.
Blog dissections
Deeply technical engineering writing, taken apart and redrawn in plainer language.
Cursor: Git at any scale
Why Git repositories resist being distributed, what GitHub's Spokes did about it, and how a write-ahead log in an object store replaces three-phase commit.7 topicsOpenAI: ten thousand agents on a Navier-Stokes result
What was actually claimed and what was not, the shape of a ten thousand agent run, the message and token economics, and why a Lean proof settles less than it appears to.6 topicsCase studies
How Netflix, Uber and others actually built it.
Netflix
Ten subsystems behind pressing play: encoding, delivery, licensing, failure, and the data that decides what you see.10 topicsUber
Matching riders to drivers over real geography: indexing the world, dispatching against it, and keeping the money correct.8 topicsTwitter and the feed
Fan-out on write against read, the celebrity problem, ranking, and the graph underneath it all.5 topicsThe classic designs
URL shortener, rate limiter, ticket booking, file sync, distributed cache, notifications. The six that come up most.6 topicsPayments: charging a card without charging it twice
Authorisation and capture, idempotency under retries, a ledger that must balance, and outcomes that arrive later.6 topicsWeb search: crawl, index, rank
Crawling a web nobody controls, an index too large for one machine, and a query that is as slow as its slowest shard.6 topicsSystem design
The building blocks, and when each one is the wrong choice.
Caching and Redis
Strategies, invalidation, TTLs, edge caching, and what actually goes wrong at scale.6 topicsLoad balancing and traffic
Spreading requests, and what breaks when a node disappears.4 topicsQueues and asynchronous work
Decoupling, delivery guarantees, and the ordering problem nobody mentions.5 topicsReplication, sharding and consistency
Scaling past one database, and what you give up when you do.4 topicsRate limiting and resilience
Timeouts, retries, breakers, limits and degradation: staying up when a dependency does not.5 topicsObservability
Logs, metrics, traces, percentiles, error budgets and alerts that are worth waking up for.5 topicsAPI design
REST, GraphQL, gRPC, webhooks and versioning, and which problem each one actually solves.5 topicsReal-time and push
WebSockets, SSE, polling and pub/sub, and how to scale a connection you keep open.3 topicsSearch and ranking
Inverted indexes, relevance, and why your database LIKE query does not scale.4 topicsStorage and media
Object storage, uploads, and delivering video without paying for it twice.3 topicsIdentity, auth and security
Sessions, tokens, OAuth, and the mistakes that become incidents.4 topicsCoordination and distributed state
Leader election, consensus, distributed transactions and unique ids.4 topicsData pipelines and analytics
Batch, streaming, OLTP versus OLAP, and getting data out without hurting production.3 topicsEvent-driven architecture
Events against commands, the outbox, choreography and the debugging problem nobody mentions.4 topicsGateways, proxies and service meshes
What belongs at the edge, what belongs beside each service, and what a mesh actually buys.3 topicsMachine learning systems in production
Serving, features, drift and evaluation, treated as an operational problem rather than a modelling one.3 topicsComputing at the edge
What moves to the edge, what cannot, and the constraints that make edge code a different runtime.3 topicsTransactions and isolation
MVCC, snapshot isolation, write skew, and the anomalies your default level allows.4 topicsQuorums, PACELC and failure domains
Leaderless replication, the part of CAP nobody quotes, and containing blast radius.4 topicsEngineering practice
Testing, security, code quality, and how teams actually work.
Testing
What to test, at which level, and why coverage is a poor target.3 topicsHow teams work
Waterfall, agile, scrum, kanban, what each assumes and when it breaks.4 topicsDesign and code quality
Patterns, coupling, and technical debt as a deliberate choice.3 topicsApplication security
Injection, XSS, CSRF, SSRF, the failures that turn a bug into a breach.5 topicsDelivery and infrastructure
Getting it running, and keeping it running.
Programming
The concepts every language shares, and the languages worth knowing properly.
Programming foundations
The concepts every language shares, explained through what they cost rather than what they look like.6 topicsPython
The data model, the mutable default, the GIL, and the parts of the language that catch experienced people.5 topicsJavaScript and TypeScript
The event loop, closures, coercion, and what TypeScript actually checks.5 topicsSQL
Joins, indexes, plans and the queries that get slow at a million rows.5 topicsJava and the JVM
Bytecode and warm-up, collections, garbage collection, virtual threads, and what erasure costs.5 topicsGo
Goroutines and the scheduler, channels, implicit interfaces, errors as values, and context.5 topicsFoundations
What everything else assumes you already know.
Networking and the web
What actually happens between a browser and your server, and where the time goes.5 topicsData structures and complexity
The handful that come up constantly, and how to talk about cost without hand-waving.4 topicsDatabases and data modelling
Transactions, indexes, normalisation, and choosing between relational and document stores.5 topicsConcurrency and operating systems
Threads, processes, async, and the bugs that only appear under load.4 topicsInterview preparation
Senior and staff level: what is being assessed, and how to show it.