Why do not all use Serializable? How does the isolation level affect performance?

The Serializable isolation level provides maximum transaction isolation, preventing anomalies such as phantom reads, non-repeatable reads, and dirty reads. However, it requires locks or other synchronization mechanisms, which significantly reduce system concurrency and performance.

Therefore, not everyone uses Serializable, especially in high-load systems where processing speed is crucial. Lower isolation levels (Read Committed, Repeatable Read) are often chosen, which strike a balance between data integrity and performance.

Impact of isolation level on performance:

• Serializable: maximum isolation, low performance due to locking.
• Repeatable Read: prevents non-repeatable reads, better performance.
• Read Committed: prevents dirty reads, high performance.
• Read Uncommitted: minimal isolation, maximum performance, but anomalies are possible.

The choice of isolation level depends on data integrity requirements and acceptable levels of concurrency.