Netflix open sourced their cloud gateway:

The Cloud Gateway team at Netflix runs and operates more than 80 clusters of Zuul 2, sending traffic to about 100 (and growing) backend service clusters which amounts to more than 1 million requests per second.

Pretty impressive. Click through to get the details of how Zuul 2 works and how they use it inside Netflix. I love when companies who are operating at webscale (😏) share their practices and code with the rest of us.