Explain Write Concern in MongoDB.

Updated May 1, 2026

Short answer

Write concern describes the level of acknowledgment requested from MongoDB for write operations.

Deep explanation

Options include 'w: 1' (primary ack), 'w: majority' (majority of replica set), and 'j: true' (on-disk journal ack).

Real-world example

Ensuring critical financial transactions are committed to a majority of nodes.

Common mistakes

Using 'w: majority' for low-priority logs, which increases latency unnecessarily.

Follow-up questions

What is 'wtimeout'?

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