Decide on a scalable quilt_rails architecture

[GoodForOneFare]

Overview

quilt_rails should have a recommended architecture that scales far beyond its current limitations.

For now, this discussion will happen in internal channels. Ping me in Slack if you'd like more context.

Motivation

Deadlocks in Puma (see #1059 for more information).

[GoodForOneFare]

We've decided to solve deadlocks via deployment configuration. Production platform will get back to us with a recommended approach. Until then, this is blocked.

[GoodForOneFare]

This is a rough version of the architecture that we'll work towards with prod eng:

There'll be some improvements along the way, of course.

[marutypes]

Closing this, as the architecture is decided. Tracking in a private issue since it's Shopify specific.