MongoDB will reuse free space when documents or collections are deleted (even though the storageSize stat will remain the same). You can compact the database to

MongoDB will reuse free space when documents or collections are deleted (even though the storageSize stat will remain the same). You can compact the database to release free space to the OS. You can read more about how MongoDB's WiredTiger storage engine reclaims space here: https://docs.mongodb.com/manual/faq/storage/#how-do-i-reclaim-disk-space-in-wiredtiger https://docs.mongodb.com/manual/faq/storage/#how-do-i-reclai... I work for MongoDB so if you have any questions about storage, feel free to reach out.