Context

Mongot recently added explicit rejection error code responses for load-shedding overload rejections, currently using:

• code: 462
• codeName: IngressRequestRateLimitExceeded

Relevant context and discussion:

• Slack thread: https://mongodb.slack.com/archives/C0A7YB2TS00/p1772234503880429
• Mongot PR (current implementation): https://github.com/10gen/mongot/pull/5412
• Design doc section: https://docs.google.com/document/d/169XkUFdGHDwNgRXHzyNdVGbJoI2mc0dwPGN4uME3Q-Q/edit?tab=t.0#heading=h.dvhatg18fpia
• Proposal section: https://docs.google.com/document/d/169XkUFdGHDwNgRXHzyNdVGbJoI2mc0dwPGN4uME3Q-Q/edit?tab=t.nwouqivvuax#heading=h.fnrry323msyr

Problem

IngressRequestRateLimitExceeded is semantically tied to ingress rate limiter behavior, and may be too specific/misleading for mongot load-shedding query rejection.

Today, retry behavior is primarily governed by labels (SystemOverloadedError, RetryableError), so error code serves mainly as canonical diagnostics and contract clarity.

Request

Define and add a dedicated MongoDB error code for mongot overload rejection, with categories aligned to overload+retry semantics:

• SystemOverloadedError
• RetriableError

Expected follow-up once available:

1. Mongot switches explicit rejection response from 462 to the new code.
2. Existing labels remain unchanged.
3. Any server-side handling/docs relying on overload code semantics can reference this dedicated code.

Suggested acceptance criteria

• New error code is added to mongo error code definitions.
• Code has clear name/description indicating mongot overload rejection.
• Categories include SystemOverloadedError and RetriableError.
• Release notes / changelog impact is documented as needed.

Notes

This ticket is for adding the code in mongo. Mongot has already reserved a local placeholder constant and can flip over once server-side code is available.