AWS Developer Associate (DVA-C01) Review Material – API Gateway

General

• Supports the following protocols:
  • REST
  • HTTP
  • WebSocket
• API Types:
  • HTTP
  • WebSocket
  • REST
  • REST (private)

REST

• Has:
  • End Points
  • Resource
  • Methods
    • Integration Type
      • Lambda (AWS_PROXY)
      • HTTP (HTTP or HTTP_PROXY)
      • Mock
      • VPC Link
      • AWS Service (AWS)
    • Proxy Integration
• End Points:
  • Edge-optimized – API Gateway API that is deployed to the specified Region while using a CloudFront distribution.
  • Private API endpoint – An API endpoint that is exposed through interface VPC endpoints and allows a client to securely access private API resources inside a VPC. .
  • Regional API endpoint – The hostname of an API that is deployed to the specified Region and intended to serve clients, such as EC2 instances, in the same AWS Region.
• Resources:
  • You expose addressable resources as a tree of API Resources entities, with the root resource (/) at the top of the hierarchy.
  • The root resource is relative to the API’s base URL, which consists of the API endpoint and a stage name.
    • {api-id}.execute-api.{region}.amazonaws.com/{stage name}
  • In the API Gateway console, this base URI is referred to as the Invoke URI and is displayed in the API’s stage editor after the API is deployed.
  • Hierarchy:
    • {Resource}/{Method} or {Resource}/{Sub Resource}/{Method} e.g.
      • /GET – The GET method of root
      • /doc/GET – The GET method of /doc
• Integration:
  • Types:
    • Lambda
    • HTTP
    • Mock
    • VPC Link
    • AWS Service
  • Integration Request
    • Encapsulates an HTTP request received by the backend. 
    • Proxy Integration:
      • Only available for Lambda and HTTP
      • If selected, input and output cannot be transformed.
      • Lambda Proxy Integration –  API Gateway passes the incoming request from the client as the input to the backend Lambda function.
      • HTTP Proxy Integration – passes the incoming request from the client to the HTTP endpoint and passes the outgoing response from the HTTP endpoint to the client.
  • Timeout: Default is 29000 ms (50ms – 29 secs)
  • Can specify execution role
  • Mapping Template:
    • A script expressed in Velocity Template Language (VTL) and applied to the payload using JSONPath expressions.
    • Can modify requests, body, or add headers
    • Can modify response
    • Use case: Convert JSON payload to XML payload for a SOAP backend API.
• Stages:
  • A named reference to a deployment, which is a snapshot of the API.
  • Configurations:
    • Cache
    • Throttling
    • WAF
    • Certificate
    • Logs/Tracing
    • Stage Variables
    • SDK
    • Export to Swagger or OpenAPI 3
    • Canary Deployment
• Stage Variables:
  •  A name-value pairs that you can define as configuration attributes associated with a deployment stage of a REST API.
  • Expression: ${stageVariables.<variable_name>}
  • Mapping Template: { "name" : "$stageVariables.<variable_name>"}
• Canary Deployment:
  • Is a software development strategy in which a new version of an API (as well as other software) is deployed for testing purposes, and the base version remains deployed as a production release for normal operations on the same stage.
  • Is defined by stages
  • Procedure:
    • Create a Canary at the stage
    • Deploy the new version to ‘Canary’
    • When ready, promote the new version
• Caching:
  • Defined by stages
  • Must define cache capacity: Min 0.5 GB to Max 237 GB
  • Define the TTL; Default to 300 s
  • A client can invalidate a cache but need to grant InvalidateCache
• Resource Policy:
  • Control whether a specified principal (typically an IAM user or role) can invoke the API. You can use API Gateway resource policies to allow your API to be securely invoked by:
    • Users from a specified AWS account.
    • Specified source IP address ranges or CIDR blocks.
    • Specified virtual private clouds (VPCs) or VPC endpoints (in any account).
• Usage Plans:
  • To configure a usage plan
    1. Create one or more APIs, configure the methods to require an API key, and deploy the APIs to stages.
    2. Generate or import API keys to distribute to application developers (your customers) who will be using your API.
    3. Create the usage plan with the desired throttle and quota limits.
    4. Associate API stages and API keys with the usage plan.
    5. Callers of the API must supply an assigned API key in the x-api-key header in requests to the API.
• Authentication and Authorization:
  • IAM using SIGv4 (AuthZ and AuthN)
  • Resource Policy (AuthZ)
  • Lambda Authorizer (AuthZ)
  • Cognito User Pool (AuthN)
• Web Sockets:
  • JSON messages are directed to backend integrations based on routes that you configure. (Non-JSON messages are directed to a $default route that you configure.)
  • There are three predefined routes that can be used: $connect, $disconnect, and $default. In addition, you can create custom routes.
    • $connect route – when a persistent connection between the client and a WebSocket API is being initiated.
    • $disconnect route – when the client or the server disconnects from the API.
    • custom route – after the route selection expression is evaluated against the message if a matching route is found; the match determines which integration is invoked.
    • $default route – if the route selection expression cannot be evaluated against the message or if no matching route is found