API Management

API Management Overview
API Management - the art of funnelling traffic from an API client through to the background service and taking care of things like authentication, rate-limiting, logging, auditing etc.
There are lots of solutions out there - both FOSS and commercial.
Google Solutions
Google have three solutions that they discuss on their cloud platform docs site (mirror):
ApiGee - looks like the super expensive enterprisey option not really an option for new products
API Gateway - seems to just provide a gateway that allows the internet to
Cloud Gateway - seems to be a really customisable/complex version of API Gateway
Seems like API Gateway might be useful if you are running cloud functions. Apigee is SOO SOO expensive - it starts at $700/month.
FOSS Solutions
Started exploring from this list (mirror) :
Looked at API Umbrella - it seems like they haven't; made any releases since 2019 and I'm not sure how maintained it is so staying away for now.
Started playing with Kong Gateway - it is lightweight, stores data in Postgres and looks easy to use with docker-compose.

Kong Gateway
Kong Gateway is an open core project that offers many of the traditional API Management features.
Minimal Docker Compose for Kong
version: "3.0"
services:
  kong:
    env_file: .env
    image: kong/kong-gateway:3.0.1.0
    environment:
      - KONG_DATABASE=postgres
      - KONG_PG_HOST=db
      - KONG_PG_DATABASE=kong
      - KONG_PG_USER=postgres
      - KONG_PG_PASSWORD=${POSTGRES_PASSWORD}
      - KONG_ADMIN_LISTEN=0.0.0.0:8001
      - KONG_ADMIN_GUI_URL=http://localhost:8002
    ports:
      - 8000:8000 
      - 8443:8443 
      - 8001:8001 
      - 8444:8444 
      - 8002:8002 
      - 8445:8445 
      - 8003:8003 
      - 8004:8004 
  db:
    env_file: .env
    image: postgres
    restart: always
    volumes:
      - ./postgres:/var/lib/postgresql/data 
    ports:
      - 5432:5432
      
  adminer:
    env_file: .env
    image: adminer
    restart: always
    ports:
      - 8080:8080
And accompanying 
.env file:
POSTGRES_PASSWORD=example
KONG_PASSWORD="supersecret123"
Docker Compose Installation
The official documentation for the project provides a walkthrough for docker installation here
Seed the Database
docker-compose run kong kong migrations bootstrap
Starting Kong
docker-compose up -d kong
Kong Config and Environment Variables
Kong normally reads a config file called 
kong.conf - an overview of valid configuration settings/directives can be found here
The docker image can read these variables from the environment. Simply copy the name of the thing, upercase it and prefix with 
KONG_ e.g. 
prefix becomes 
KONG_PREFIX.