Rate limiter: Fastly Edge Rate Limiting, and an in-memory backend for Axum (after the MVP) #477

Summary

Rate limiter: Fastly Edge Rate Limiting, and an in-memory backend for Axum (after the MVP).

Behavior

A limiter with Fastly Edge Rate Limiting and an in-memory backend for Axum, then Cloudflare and Spin backends per DEC-15.

Acceptance criteria

• A contract test passes per backend

Dependencies

Blocked by:

• PR feat: implement portable outbound HTTP and request lifecycle contracts #275 feat: implement portable outbound HTTP and request lifecycle contracts

Waits on these decisions:

• DEC-15 Rate limiting after the MVP (open). Rate limiting is punted past the MVP: the keys (batch sync stays per partner), EdgeZero's limiter with its Cloudflare and Spin backends, and new limits on record creation and on Axum. Blocks EZI-5, EZI-5c, EZI-5s and T10.

Blocks:

• Rate limiter backend for Cloudflare (after the MVP) #481 Rate limiter backend for Cloudflare (after the MVP) (new in this plan)
• Rate limiter backend for Spin (after the MVP) #487 Rate limiter backend for Spin (after the MVP) (new in this plan)
• Rate limits after the MVP trusted-server#1590 Rate limits after the MVP (new in this plan)

Related

• Needed by Server-side identity on every adapter trusted-server#1558, server-side identity on every adapter. Planned in an any row (no fixed wave; starts when its decision or reviewer is ready; after the MVP); priority P3, size S.
• Requirement EZI-5 in the design.