Graceful Degradation
Problem
Your recommendation engine fails.
Should your entire online shop now return:
500 Internal Server Error
even though browsing and purchasing still work?
Solution — Graceful Degradation
Design non-essential failures to reduce functionality rather than destroy the entire service.
Shop ✓
Checkout ✓
Search ✓
Recommendations ✗
Core idea: graceful degradation preserves useful functionality when optional capabilities fail.