Why APIs Slow Down Over Time
Many APIs start fast and then degrade as data grows. The most common reason is missing or misaligned indexes.
Start With Query Patterns
Index design should follow real query patterns, not assumptions.
Ask:
- Which columns appear in WHERE?
- Which columns appear in ORDER BY?
- Are filters selective?
Useful Index Types
- B-tree for general equality/range queries
- GIN for JSONB and full-text search
- Partial indexes for filtered subsets
- Composite indexes for frequent multi-column filters
Pick indexes based on workload, not preference.
Validate With Explain Plans
Always check plans after index changes:
- Are index scans being used?
- Is row estimate accurate?
- Is sort cost reduced?
Measure with production-like data volume.
Watch Write Cost
More indexes speed reads but slow writes.
Monitor:
- Insert/update latency
- Vacuum behavior
- Index bloat
Performance is a read-write trade-off.
Final Thought
Good indexing is one of the highest-ROI backend optimizations. Design from query patterns, validate with plans, and keep indexes lean.