.NET Architecture & System Design Interview Question #78

What are transaction isolation levels?

Transactions, CQRS, Event Sourcing & Distributed Consistency Mid-Level Intermediate

Quick Interview Answer

Transaction isolation levels control how much one transaction can observe or interfere with concurrent transactions. Common relational levels include Read Uncommitted, Read Committed, Repeatable Read, and Serializable; some databases also provide snapshot-based isolation.

Detailed Explanation

Transaction isolation levels control how much one transaction can observe or interfere with concurrent transactions. Common relational levels include Read Uncommitted, Read Committed, Repeatable Read, and Serializable; some databases also provide snapshot-based isolation.

Stronger isolation can simplify correctness but may increase blocking, retries, or resource usage. The appropriate level depends on the anomalies the business operation must prevent.

Code Example

Lower isolation
    -> more concurrency
    -> more possible anomalies

Higher isolation
    -> stronger guarantees
    -> potentially more contention