T77 Dec 24, 2025 3 min read

Database

A persistent datastore used to store and query structured data with defined semantics around consistency and durability.

Definition

A database is a system for storing and querying data.

In system design, the database is often the thing that sets your scaling and consistency constraints.

Questions that matter

  • What is the primary key and access pattern.
  • What is the growth rate.
  • What consistency does each flow need.
  • Do you need multi-region, and what does that imply.