4: API Gateway

What is API Gateway?

• Make your own REST or websocket APIs
• Connect programmers (via HTTP GET and POST requests) to:
  • Lambdas
  • DynamoDB
  • Ec2
  • S3
  • Caches
  • Cloudwatch
  • Etc.

REST vs Websockets?

• REST: 1-way comms; simple request/response
• Socket: 2-way comms; e.g. update the GUI as we go
  • Backend service can initiate comms
  • Real-time chat is one good example

Authentication?

• Web identity federation stuff

What about HTTP APIs?

• Cheaper and faster than REST
• Still lacking full functionality of REST
• Go with HTTP unless you need those extra functionalities

What’s Lambda Proxy Integration?

• You can proxy requests as-is to lambda funcs
• You can point API Gateway to lambda aliases
  • E.g. point to “prod” rather than “version 2”
• You have to give API gateway permission to invoke a lambda function
  • The function has a resource-based policy to allow this

How is the API updated automatically?

• When you add an API to your function—
  • …via lambda console,
  • …via API gateway console,
  • …or via SAM template,
• The resource-based policy is updated automatically.