Clients send request our microservices by making HTTP API calls. Ideally, our clients should have a tightly bounded service contract to our API in order to achieve consistent expectations of microservice responsibility.

Amazon API Gateway hosts RESTful HTTP requests and responses to customers. In this scenario, API Gateway provides built-in authorization, throttling, security, fault tolerance, request/response mapping, and performance optimizations.

AWS Lambda contains the business logic to process incoming API calls and leverage DynamoDB as a persistent storage.

Amazon DynamoDB persistently stores microservices data and scales based on demand. Since microservices are often designed to do one thing well, a schema-less NoSQL data store is regularly incorporated.

https://medium.com/aws-lambda-serverless-developer-guide-with-hands/build-crud-restful-microservices-with-aws-lambda-api-gateway-dynamodb-with-aws-sdk-js-v3-408fa2f85048