Reliability

LLMs are fluent text generators; production systems need contracts. The gap shows up when a classifier returns urgent-ish, omits a required field, wraps JSON in…

An order database's primary data center suffers a catastrophic, unrecoverable event — not a transient node failure, an actual disaster. Two numbers now determin…

A team deploys their application to three regions, each with its own app tier, database, and network path. On paper, a failure in one region should never touch …

A permission check in front of a wire-transfer approval endpoint times out. What should happen next? One engineer's instinct says "don't block the transfer over…

A payment service keeps processing requests with zero dropped transactions while one of its three nodes crashes mid-request — that's fault tolerance. A differen…

A product page shows the item, its price, and an "add to cart" button — the core path — plus a "customers also viewed" recommendation strip powered by a separat…

A checkout API runs three replicas across two availability zones behind a load balancer — on paper, no single point of failure. Then one AZ has a networking inc…

An order-ingestion API writes to an in-memory queue, a worker pool drains it, and a payment provider on the other end gets slow. The queue keeps accepting every…

A checkout API can wait until every step finishes, or accept an order and complete work later. The first path gives the caller an immediate final answer but cou…

An order API can return responses all day and still charge the wrong amount. It can be temporarily unreachable while every stored order remains safe. It can fai…

A team sets an internal reliability target of 99.9% and signs a customer contract promising 99.5% — and a new engineer immediately asks why the numbers don't ma…