ResourceNotFoundException: Requested resource not found

What it means

ResourceNotFoundException is one of the most-encountered errors in AWS and one of the least informative, because the thing it most often means is the thing it cannot say. The service checked for the resource you named, in the account it was called from and the region it was called in, and did not find it. It has no way of knowing the resource exists perfectly well somewhere else.

Region is the usual answer. An SDK client constructed without an explicit region takes it from AWS_REGION, which the execution environment sets to wherever the function is deployed. That is almost always what you want, and it means the same code targets us-east-1 in one deployment and eu-west-1 in another without anything in the source suggesting a region is involved. Code developed against a hardcoded region, or a client copied from a script that set one, changes behaviour on deploy in a way nothing in the diff shows.

The second recurring cause is a name that is empty. An environment variable that was never set resolves to undefined, gets passed as the table or queue name, and produces a not-found for a resource with no name at all. Read closely, the message often shows this — there is simply nothing between the colon and the words "not found" — but it reads as a formatting quirk rather than as the answer.

The subtlety worth carrying is that not-found and access-denied are not always distinct. Several AWS services deliberately return ResourceNotFoundException when the caller has no permission to know the resource exists, because confirming existence to an unauthorised caller is itself a small information leak. So a resource you can see in the console, in the right account and the right region, that the function insists is not there, may be a permissions problem wearing a not-found message. Checking the execution role before assuming a deployment problem is worth the minute it takes.

What it looks like in CloudWatch

This is the shape the failure arrives in: the lines of one invocation scattered among everything else the log group received at the same moment.

The panel on the right is generated by running the excerpt on the left through the same parser that powers the free web stitcher — it is what the tool actually produces for this input, not an illustration of it.

How to confirm it from the logs

Read the resource identifier in the message and check its region and account. If it is an ARN, both are in it and the comparison is direct. If it is a bare name — a table, a queue, a secret — the region is implicit in the client's configuration, which means the message cannot show you the thing most likely to be wrong.

Distinguish it from a permissions failure, because the two are easy to confuse and IAM sometimes chooses this deliberately. AccessDeniedException says you may not; ResourceNotFoundException says there is nothing there. But some services return not-found rather than denied when the caller has no permission to know the resource exists, so a resource you can see in the console and the function cannot find is worth checking as a permissions problem too.

Causes, most likely first

Fixes

jsconsole.log("config", {
  region: process.env.AWS_REGION,
  table: process.env.TABLE_NAME,
  function: process.env.AWS_LAMBDA_FUNCTION_NAME
});

jsfunction required(name) {
  const value = process.env[name];
  if (!value) throw new Error(`${name} is not set`);
  return value;
}

// Module scope: fails once, loudly, rather than per request and obscurely.
const TABLE_NAME = required("TABLE_NAME");

yamlResources:
  OrdersFunction:
    Type: AWS::Serverless::Function
    Properties:
      Environment:
        Variables:
          TABLE_NAME: !Ref OrdersTable
          QUEUE_URL: !Ref OrderQueue

jsconst client = new DynamoDBClient({ region: process.env.TABLE_REGION ?? process.env.AWS_REGION });

Also seen as

The same underlying failure, worded differently by a different runtime, SDK version, or logging layer. All of these land here — there is no separate page for each phrasing.

Related errors

Errors that show up alongside this one, or that people mistake for it.

References

• AWS Lambda Developer Guide — Lambda runtime environment variables
• Amazon DynamoDB Developer Guide — Error handling