How to carve a growing Rust codebase into crates and modules that a team can still reason about.
Backpressure is how a slow consumer tells a fast producer to slow down. Without it, queues grow until memory runs out. Rust's bounded channels and semaphores make it explicit.
A service that stays up by doing less beats one that tries to do everything and falls over. Decide in advance what to drop and how to say no quickly.
In-process limiters count per instance, so ten replicas allow ten times the limit. A shared counter in Redis makes the limit global, at the cost of a network hop and a failure policy.
An actor is a task that owns its data and processes messages one at a time. Channels replace locks, and a handle type hides the plumbing.
An event bus lets parts of a program react to things without knowing about each other. Tokio's broadcast channel gives a small, typed one with built-in handling for slow subscribers.
Split work across a bounded pool of workers and merge the results: a producer, bounded channels for backpressure, N workers, a collector and clean shutdown. A Tokio pipeline with ordering, errors and cancellation handled.
Logs, metrics and traces answer different questions. Wire them together with tracing and OpenTelemetry in a Rust service: one instrumentation API, a collector, context propagation across services and sensible sampling.
Stop one failing dependency from taking the whole service down. A circuit breaker fails fast after repeated errors and probes for recovery; a bulkhead caps concurrency per dependency. Implement both with Tokio.
Build a reliable job queue in a single table: claim rows with FOR UPDATE SKIP LOCKED, mark them done in the same transaction, retry failures with backoff, and know where this stops scaling.
Pick a background job system for a Rust service: an in-process Tokio channel, a database table with SKIP LOCKED, Redis queues, or a broker. Compare durability, retries, scale and operational cost.
Write the database change and the event it should publish in one transaction, then publish from an outbox table with a relay. Fixes the dual write problem in Rust with SQLx.
Make POST requests safe to retry: clients send an Idempotency-Key, the server stores the first result keyed on it and replays it. An Axum and SQLx implementation with edge cases.
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