Amazon & AWS DevOps System Design & Architecture interview questions

Stateless does not mean there is no state. It means the state is not in the instance, which is what lets you kill any instance at any time. Every scaling and deployment property people want depends on that one thing.

It converts a synchronous failure into a delay. That is the whole benefit and the whole cost, because the caller now gets an answer before the work has happened and somebody has to tell them when it did.

The classic napkin-math question. The number in the prompt is the question. Drawing the architecture before doing the arithmetic produces a design the physics forbids, and the arithmetic takes a minute.

The Indian e-commerce interview question, and autoscaling is the wrong first answer. A 10x spike arriving in seconds outruns any scaling loop, so the design has to absorb rather than scale.

Every candidate says replication and failover. The scoring answer names the replication mode, states the resulting data loss window, and explains how the cluster avoids two primaries.

The Google-style NALSD round in miniature. The boxes are easy; what is being scored is whether the numbers fall out of Little's law before you draw them.

The catalog is the easy half. The scored half is stampede dynamics: one hot key expiring can multiply origin load by a thousand in a second, and there are three distinct fixes.

The most rehearsed design question, which is exactly why the interesting parts are the ones blog posts skip: redirect semantics, key generation under failure, and analytics kept off the hot path.

The vocabulary question hiding real depth: which primitive replaces ORDER BY, why sharding by player is wrong, and what a 45,000 updates-per-second storm actually costs.

Type-ahead is a latency budget wearing a search costume: keystrokes arrive every 200 milliseconds, so anything slower feels broken. Prefix indexes, freshness tiers, and typo tolerance are the scored parts.

Size stored sessions from expiry and creation rates, then decide how quickly logout must take effect and what failover may forget.

Ladders and player logic are the warm-up. Cache topology, egress arithmetic, and knowing which quality metric actually predicts churn are what separate the answers.

A disputed invoice needs a reproducible calculation. Retain raw usage events and versioned pricing so each line can be explained and corrected.

DNS time-to-live is a suggestion and nineteen minutes is what believing it costs. The mechanism you choose decides your failover time, and the health check you choose decides whether it fires at all.

The design round where the honest answer is mostly about data. Stateless traffic across regions is straightforward; the database is where active-active is either solved or pretended.

Drawing an agent that polls a server is the easy third. The interview is about partial applies, fleet-versus-world state, and why rollback must be a pointer flip, never a reverse edit.

The migration question, and the trap is answering with a target architecture. What is being scored is sequencing: how you get there without a rewrite and without a release freeze.

The default answer is 'horizontal' because interviews reward it. The correct answer names the constraint that makes distribution expensive and knows when one big machine is the engineering choice.

Everyone names token bucket. The scored part is the rest: drift between nodes, the 429 contract with clients, and whether your quota service should fail open or closed.

Cron is the most-deployed scheduler on earth and the worst-behaved at scale. The scored content is everything crontab cannot do: exactly-once firing, thundering herds, and what happens when the scheduler itself dies.