Excessive or duplicate indexes degrade write performance and storage
6/10 MediumUnused or duplicate indexes cause every database modification to unnecessarily update those indexes, resulting in high storage utilization and IOPs consumption. This creates a silent performance drag that isn't immediately obvious.
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A common mistake is either not using indexes at all or using them incorrectly... Adding too many indexes can slow down write operations because every INSERT, UPDATE, or DELETE operation needs to update the indexes.
You should have indexes to optimize all of your frequent queries, but use the wrong type or too many of them and things could backfire. 15 indexes on one collection is on the high side and could slow down your writes... those 15 indexes are consuming 85 GB of space. With the 4 GB of cache available on their M30 Atlas nodes, that's a huge problem!
if you have more indexes which are unused or duplicate, every modification to the database will lead to update those unnecessarily, which is where you see storage and I obstacleization.