ConfigError: Missing region in config

TL;DR — The AWS SDK doesn't know which region to talk to. Set it explicitly on the client (new DynamoDBClient({ region: 'us-east-1' })), or via the AWS_REGION environment variable, or in ~/.aws/config.

What it means

ConfigError: Missing region in config

Every DynamoDB endpoint is regional, so the SDK must resolve a region before it can send a request. When none of its configuration sources supplies one, it throws this before any network call.

Why it happens

• No region passed to the client and no AWS_REGION / AWS_DEFAULT_REGION in the environment.
• No default region in ~/.aws/config for the active profile.
• Running in a context without instance/role metadata (a local script, some CI runners) where the SDK can't infer a region.
• A typo in the env var name (AWS_REGIONS, REGION).

How to fix it (any one of these)

1. Set it on the client (most explicit):

   import {DynamoDBClient} from '@aws-sdk/client-dynamodb';
   const client = new DynamoDBClient({region: 'us-east-1'});

2. Environment variable:

   export AWS_REGION=us-east-1

3. AWS config file (~/.aws/config):

   [default]
   region = us-east-1

4. DynamoDB Local? It still needs a region string (any value) plus an endpoint:

   const client = new DynamoDBClient({region: 'local', endpoint: 'http://localhost:8000'});

Related errors

• The security token is invalid
• ResourceNotFoundException — often a region mismatch once a region is set.
• Unable to start DynamoDB Local process