The Bottleneck
# Before: naive approach — O(n²) lookup
def find_user(users, uid):
for user in users: # 💀 scans entire list
if user.id == uid:
return user
# After: hash map — O(1)
user_index = {u.id: u for u in users}
def find_user(uid):
return user_index.get(uid) # ⚡ instant