7 MongoDB indexing strategies to speed up your queries

MongoDB is fast by default, until it isn't. Once your collections grow past a few hundred thousand documents, unindexed queries start doing full collection scans, and latency climbs fast. Indexes are the single most impactful thing you can do to fix this. But MongoDB gives you a lot of index types, and picking the wrong one — or using the right one incorrectly — can leave performance on the table or even make things worse. This guide covers seven indexing strategies that actually matter in practice, with concrete examples and the tradeoffs you need to know. 1. Single field indexes Single field indexes are the starting point. You create one on a field you query or sort frequently, and MongoDB uses it instead of scanning every document. db . orders . createIndex ({ customerId : 1 }) The 1 means ascending order; -1 means descending. For most equality queries this doesn't matter much, but for range queries and sorts it can. If you're sorting by createdAt DESC , an index with -1 will work w