System Design

A message queue promises to deliver messages, but the promise has terms — at-least-once, at-most-once, ordering, and retries — and…

Splitting a system into services makes boundaries expensive to change. Getting them wrong produces a distributed monolith that is harder…

Splitting a monolith into separate deployable services while leaving them all reading and writing the same database preserves every coupling…

A load balancer does more than spread traffic — it is the mechanism for handling failures and for managing state,…

A dependency that is struggling under load gets a flood of retries from every caller treating each failure as transient,…

Caching improves performance by serving stale data, and the trade-off between freshness and speed should be a deliberate decision, not…

Event sourcing stores the history of changes rather than the current state, which gives a complete audit trail and the…

Adding a queue between a fast producer and a slow consumer feels like it solved the throughput mismatch. Without backpressure,…

Sharding spreads data across many databases to scale, but it moves the problem from one big database to a set…

Networks fail after the request arrives but before the response returns. Without idempotency, your retry logic is a duplicate-charge generator.