Error: Conditional Update Error DynamoDB

A conditional update fails with ConditionalCheckFailedException when its condition evaluates to false. DynamoDB leaves the item unchanged. This can be the intended protection against stale writes or updates to a missing item.

import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import { DynamoDBDocumentClient, UpdateCommand } from "@aws-sdk/lib-dynamodb";

const db = DynamoDBDocumentClient.from(new DynamoDBClient({}));

await db.send(new UpdateCommand({
  TableName: "Orders",
  Key: { pk: "CUSTOMER#123", sk: "ORDER#42" },
  UpdateExpression: "SET #status = :next",
  ConditionExpression: "#status = :expected",
  ExpressionAttributeNames: { "#status": "status" },
  ExpressionAttributeValues: { ":next": "SHIPPED", ":expected": "PAID" },
  ReturnValuesOnConditionCheckFailure: "ALL_OLD",
}));

Check the complete key, attribute type and current value. Missing attributes, String versus Number differences, or another writer changing the state can explain the failure. Where supported, ALL_OLD makes the failure item available in the exception; otherwise read it and remember it can change again.

Retry only after deciding the update is still valid. A version conflict usually requires reading fresh state and recomputing the change. Removing the condition merely to make the write succeed defeats the concurrency protection.

See conditional writes and AWS documentation.