System design.
How real backend systems are designed, from the naive version to production, with the data structures underneath and the trade-offs at each step.
In study order. Each article starts at beginner level, so you can begin anywhere.
Designing a rate limiter, from first idea to production
How rate limiters work, from a ten-line counter to a distributed Redis design: five algorithms, a live simulator, two classic bugs and real production code.
Idempotency and safe retries, from first idea to production
Why retries double-charge and how to stop it: idempotency keys, upserts, backoff with jitter, the outbox and inbox, with live demos and real production code.
Caching, from first idea to production
How caching works, from TTLs and cache-aside to eviction, HTTP headers, stampedes and LLM caches, with two live simulators and real production code.
Queues and backpressure, from first idea to production
How job queues work, from one producer and one worker to Little's Law, Celery tuning, retry storms and backpressure, with two live simulators and real code.
Consistent hashing, from first idea to production
How consistent hashing works, from hash % N to rings, virtual nodes, jump hash, Maglev and Redis Cluster slots, with live demos and measured numbers.
Designing real-time chat, from first idea to production
How real-time chat works: polling vs WebSockets, message ordering, receipts, presence, fan-out across servers and slow readers, with live demos and real code.