Sketch the box-level architecture.
Why not just use a database as a queue? Liu provides the killer interview answer: A queue guarantees at-least-once delivery, ordering (in a single partition), and decoupling of producers/consumers. He includes a dead-letter queue (DLQ) pattern – missing from half the PDFs. Add it manually: Failed messages → DLQ → Alert + manual replay. system design interview fundamentals rylan liu pdf fix
Symptoms: The PDF mentions "Zookeeper for service discovery" but not Consul or etcd; it lacks Kubernetes or GraphQL. Non-Relational (NoSQL): (Cassandra, MongoDB, DynamoDB)
Fixes: