Advanced Reporting
Isolation Levels Explained
Senior Data Analyst
March 28, 2026
5 min read
The Levels
1. **Read Uncommitted**: Can see uncommitted changes. Risky.
2. **Read Committed**: Default in PostgreSQL. Only see committed data.
3. **Repeatable Read**: Re-reading the same row gives the same result.
4. **Serializable**: Highest isolation. Transactions run as if in sequence.
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
Pro Tip
Higher isolation = more consistency but lower concurrency. Choose wisely.
*Day 88: Locking and Deadlocks.*