gh-djankies-claude-configs-prisma-6/skills/configuring-transaction-isolation/references/database-defaults.md

Database-Specific Defaults

PostgreSQL

Default: ReadCommitted

Supported levels:

• Serializable (strictest)
• RepeatableRead
• ReadCommitted (default)

Notes:

• PostgreSQL uses true Serializable isolation (not snapshot isolation)
• May throw serialization errors under high concurrency
• Excellent MVCC implementation reduces conflicts

MySQL

Default: RepeatableRead

Supported levels:

• Serializable
• RepeatableRead (default)
• ReadCommitted
• ReadUncommitted (not recommended)

Notes:

• InnoDB engine required for transaction support
• Uses gap locking in RepeatableRead mode
• Serializable adds locking to SELECT statements

SQLite

Default: Serializable

Supported levels:

• Serializable (only level - database-wide lock)

Notes:

• Only one writer at a time
• No true isolation level configuration
• Best for single-user or low-concurrency applications

MongoDB

Default: Snapshot (similar to RepeatableRead)

Supported levels:

• Snapshot (equivalent to RepeatableRead)
• Majority read concern

Notes:

• Different isolation model than SQL databases
• Uses write-ahead log for consistency
• Replica set required for transactions