What Is Database Sharding — and When Does Your Startup Actually Need It

The article defines database sharding as horizontal partitioning across multiple database instances, and distinguishes it from replication.

It argues most startups should try simpler scaling tools first, such as indexing, caching, read replicas, pooling, and vertical scaling.

Sharding is presented as a last-resort strategy because it adds operational complexity and makes cross-shard queries and transactions harder.

The piece also highlights the importance of choosing a shard key, such as user_id, with care to avoid uneven data distribution.