Distributed Key-Value Store

Designing a distributed key-value store means building something like Dynamo or Cassandra: a simple get/put interface on top of partitioning, replication, failure detection, and conflict handling. It is a tour of nearly every distributed-systems concept in one problem.

Clarify requirements

Functional

• put(key, value), get(key), delete(key).
• Keys up to 256 B, values up to 1 MB (typically ~1 KB).
• Optional per-key TTL.
• Tunable consistency per request.

Non-functional

• Highly available for writes and reads, even during node failures and partitions (AP leaning, as for a shopping cart or session store).
• Scales horizontally to hundreds of nodes, petabytes, millions of ops/s.
• Low latency: p99 < 10 ms within a region.
• Durable: acknowledged writes survive node failure.
• Automatic recovery and rebalancing.