Isolation Levels: The Art of Transaction Privacy

Imagine two people editing the same Google Doc simultaneously. How does the system decide what each person sees and when? Databases face this exact challenge with transactions.

Isolation levels determine how much one transaction knows about another running at the same time. It's like setting privacy levels for database operations.

The Four Levels of Privacy:

1. Repeatable Read (The Consistent Friend)

• Once you read a value, you'll always see the same value in that transaction
• Like having a photographic memory - your view doesn't change mid-conversation

2. Read Committed (The Realistic Friend)

• Always sees the latest committed changes
• Your view might change if someone else finishes their work

3. Read Uncommitted (The Gossip Friend)

• Sees even unfinished work from others
• Risky - you might act on information that gets cancelled!

4. Serializable (The Overprotective Friend)

• Complete isolation - when you're working, nobody else can even look
• Safest but slowest

Key Insight: Isolation levels are about choosing between consistency and speed - stricter isolation means better data integrity but slower performance.