Idempotency, and Why Retries Need It
A network can't tell a client whether its request failed or only its reply did. Idempotent operations make that ambiguity safe to retry through.
Distributed systems
Computation spread across machines that fail independently and talk over unreliable networks.
Essays
Garden
Retries are inevitable
Over a network, a client that times out cannot know what happened. So it will retry — and the system must be built to survive that.
Lab
Backoff and Jitter Playground
Adjust an exponential backoff schedule and watch what happens when two dozen clients retry at once — with and without randomness.