Indexing everything is not the flex people think it is

Early on I read “add indexes to fields you query often” and took it as index more.

Indexes help the database find rows without scanning the whole collection. They also:

• Use memory (sometimes a lot).
• Slow inserts/updates/deletes because every index must stay consistent.

So they are a trade-off, not free speed.

What I do now: index fields that appear in hot queries and where a full scan actually hurts (large collections, real user traffic). For small tables or rare admin queries, a scan is fine.

Profiling beats guessing. One explain plan tells you more than ten indexes you added “just in case.”