Polyglot Persistence

Polyglot Persistence#

In 2019, a mid-size e-commerce company ran everything on a single PostgreSQL instance. Transactional orders, full-text product search, user activity metrics, and friend-of-friend recommendation queries all competed for the same connection pool. The database didn't fail dramatically. It just got slower, then slower, then slow enough that engineers started bolting on indexes to compensate, which made writes slower, which made everything wor...