What Is a Transaction Isolation Level?

An isolation level defines the degree to which concurrent transactions are shielded from one another, from read uncommitted up through serializable. Higher levels prevent more anomalies such as dirty reads and phantom reads but allow less concurrency. Each level is a defined point on the trade-off between strict consistency and throughput.

Why it matters

Choosing the isolation level decides which read anomalies your application can encounter. Picking too low risks subtle data bugs; picking too high can throttle throughput under load.

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