Normalization & DenormalizationdebuggingIntermediate
The follower count is visibly wrong
Symptoms
- A profile shows 1,240 followers but listing the followers returns 1,207.
- The discrepancy varies per user and grows over time.
SELECT u.follower_count AS cached, count(f.id) AS actual FROM users u LEFT JOIN follows f ON f.followee_id = u.id WHERE u.id = 7 GROUP BY u.follower_count; cached: 1240 actual: 1207 drift: 33
Investigate
Inspect areas in any order (0/4 inspected). When you think you know the root cause, commit to it.
How the counter is maintained
Code paths that modify follows
Transaction boundaries
Race conditions