Databases Intermediate

What is Migration?

A version-controlled change to a database schema that can be applied and reversed systematically.

Database migrations track schema changes over time, similar to version control for code. Each migration defines an "up" (apply) and "down" (revert) operation, such as creating tables, adding columns, or modifying constraints.

Migrations ensure all environments (development, staging, production) have identical database schemas. They are run in sequence and tracked to prevent re-application. Tools include Flyway, Liquibase, Alembic, and framework-specific migration systems.

Related Terms

A middleware server that sits between applications and databases, providing connection pooling, load balancing, and query routing.

Database Connection Pooling

A technique that maintains a cache of database connections for reuse, reducing the overhead of creating new connections.

EXPLAIN ANALYZE

A PostgreSQL command that shows the execution plan of a query along with actual runtime statistics for performance tuning.

MVCC (Multi-Version Concurrency Control)

A technique where the database maintains multiple versions of data to allow concurrent reads and writes without locking.

CTE (Common Table Expression)

A temporary named result set defined within a SQL statement using the WITH clause, improving query readability and enabling recursion.

An open-source, in-memory data store used as a database, cache, message broker, and queue with sub-millisecond response times.

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