Mongo DB - difference between standalone & 1-node replica set

Question

I needed to use Mongo DB transactions, and recently I understood that transactions don\'t work for Mongo standalone mode, but only for replica sets (Mongo DB with C# - docum

Answer 1

I think kevinadi answered well, but I still want to add it.

A standalone is an instance of mongod that runs on a single server but is not part of a replica set. Standalone instances used for testing and development, but always recomended to use replica sets in production.

A single-node replica set would have the oplog which records all changes to its data sets . This means that you'll use more disk space to store the oplog, and also any insert/update operation would be written to the oplog as well (write amplification). It also supports point in time recovery.

Please follow Convert a Standalone to a Replica Set if you would like to convert the standalone database to replicaset.

Transactions have been introduced in MongoDB version 4.0. Starting in version 4.0, for situations that require atomicity for updates to multiple documents or consistency between reads to multiple documents, MongoDB provides multi-document transactions for replica sets. The transaction is not available in standalone because it requires oplog to maintain strong consistency within a cluster.