SQL Performance Cheatsheet The Query Mistakes That Kill Databases in Production

What this is

This is not a SQL tutorial.
This is a cheatsheet of the database patterns that only become visible when your system is under real load.

It focuses on:

• Why queries that look fine become slow
• How indexes actually behave at scale
• How locking and transactions kill throughput
• Why “just add an index” often makes things worse

All explained concisely, with real-world examples and fixes.

Who this is for

• Backend engineers working with production databases
• Developers dealing with slow queries and rising cloud bills
• Teams running Postgres, MySQL, or similar relational databases

Not for beginners.

What you get

• A concise cheatsheet covering:
  • Indexing strategies and tradeoffs
  • Query plan analysis
  • Join and aggregation pitfalls
  • N+1 problems and ORM traps
  • Locking and transaction issues
  • Common slow query patterns
• Practical examples
• Concrete fixes

PDF format. Easy to search and reference.

Why this is different

Most SQL content explains syntax.
This explains failure modes.

It’s based on production incidents, not academic examples.

Format

• PDF
• ~5–7 pages
  • Instant download