My colleagues and I are working with inherited infra so please don’t judge Today we were upgrading Mongo on one of the servers - from 3.2 to 4.2. After mongodump > mongorestore we have noticed that the size of the collections has decreased by about 30% (~4GB less). We’re not that familiar with the stored data since we’re new hires but it does not look anything is missing.
Do you have any idea what could have caused that reduction in storage size? Do recent versions of Mongo store data in a more efficient way than back in 2015?