Checkpoint: Performance

Checkpoint — the N+1 rescue

db records every db.query(sql, params) call. The naive implementation makes one query PER user (N+1). Batch it:

• fetch_user_orders(user_ids, db) returns {user_id: [{'id':…, 'total':…}, …]}
• with at most 2 queries total (regardless of user count)
• order lists per user keep the row order returned by the db

This is the exact shape you will meet again in the database module — learned here as a performance pattern, applied there as SQL.