mongodb/node-mongodb-native · error · MongoInvalidArgumentError

Cannot request unacknowledged write concern and ordered…

Error message

Cannot request unacknowledged write concern and ordered writes

What it means

Thrown when bulk write options combine writeConcern w:0 (unacknowledged) with ordered: true. Because ordered writes wait for each batch to be acknowledged before sending the next, ordering is meaningless without acknowledgements; the driver requires ordered: false when w is 0.

Solutions

1. Pair w:0 with ordered: false: client.bulkWrite(models, { writeConcern: { w: 0 }, ordered: false }).
2. Or keep ordered writes by using an acknowledged write concern (omit w:0).
3. Remember ordered defaults to true — you must explicitly opt out when w is 0.

Example fix

// before
await client.bulkWrite(models, { writeConcern: { w: 0 } }); // ordered defaults to true

// after
await client.bulkWrite(models, { writeConcern: { w: 0 }, ordered: false });

if (options?.writeConcern?.w === 0 && (options?.ordered ?? true)) {
  throw new Error('w:0 requires ordered:false');
}
await client.bulkWrite(models, { ...options, ordered: options?.writeConcern?.w === 0 ? false : (options?.ordered ?? true) });

When it happens

Trigger: Calling client.bulkWrite(models, { writeConcern: { w: 0 } }) without overriding ordered — the default for ordered is true, so the check fails immediately. Same outcome if you set both w:0 and ordered: true explicitly.

Common situations: Setting w=0 in the connection string for throughput and then calling bulkWrite without options; performance tuning that drops acknowledgement but forgets to relax ordering.

Related errors

• Cannot request unacknowledged write concern and verbose…
• write operation failed
• Argument "operations" must be an array of documents
• authMechanism not supported
• Bulk find operation must specify a selector

AI-assisted analysis of mongodb/node-mongodb-native@dce7939f86 (2026-08-11). Data as JSON: /api/errors/bb2ad7334110bc80. Report an issue: GitHub.

Appendix: source

Thrown at src/operations/client_bulk_write/executor.ts:70

      bypassDocumentValidation: false,
      verboseResults: false,
      ...options
    };

    // If no write concern was provided, we inherit one from the client.
    if (!this.options.writeConcern) {
      this.options.writeConcern = WriteConcern.fromOptions(this.client.s.options);
    }

    if (this.options.writeConcern?.w === 0) {
      if (this.options.verboseResults) {
        throw new MongoInvalidArgumentError(
          'Cannot request unacknowledged write concern and verbose results'
        );
      }

      if (this.options.ordered) {
        throw new MongoInvalidArgumentError(
          'Cannot request unacknowledged write concern and ordered writes'
        );
      }
    }
  }

  /**
   * Execute the client bulk write. Will split commands into batches and exhaust the cursors
   * for each, then merge the results into one.
   * @returns The result.
   */
  async execute(): Promise<ClientBulkWriteResult> {
    // The command builder will take the user provided models and potential split the batch
    // into multiple commands due to size.
    const pkFactory = this.client.s.options.pkFactory;
    const commandBuilder = new ClientBulkWriteCommandBuilder(
      this.operations,
      this.options,

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