Transaction isolation in MongoDB is not something that a user directly configures. Instead, it is mainly handled by the MongoDB server itself.
However, MongoDB provides several options that can indirectly affect transaction isolation:
1. Read Preference: This determines the preference of reading data from primary or secondary nodes in a replica set.
1. Read Concern: This applies only to replica sets and sharded clusters. It allows clients to choose a level of isolation for their reads. The read concern “majority” allows reads that provide the most current majority-committed view of data.
1. Write Concern: This determines how MongoDB applies write operations to members of a replica set or a sharded cluster, and the acknowledgment behavior.
1. Causal Consistency: You can enable causal consistency for a MongoDB session to ensure that read and write operations reflect the order of their issuance, providing a stronger level of consistency.
1. With the introduction of multi-document transactions in MongoDB 4.0, you can execute a series of data manipulation language (DML) operations in an atomic operation.
After all, MongoDB is a non-relational, NoSQL database, and it often doesn’t have the same extensive support for finely-tuned transaction isolation that might be found in a relational database system like MySQL, PostgreSQL, or Oracle.
