[Docs] Add an indexer/realtime operational runbook (replay/reset/status, lag thresholds, RPC-outage recovery)

[grantfox-oss]

Telegram (ask questions / claim the issue here first): https://t.me/+DOylgFv1jyJlNzM0

Why this matters

docs/ has SSE_ARCHITECTURE/IMPLEMENTATION and auth/versioning docs but no indexer runbook. The admin recovery endpoints, the lag/health semantics, and the indexer env vars (INDEXER_POLL_INTERVAL_MS, INDEXER_START_LEDGER, STREAM_CONTRACT_ID) are undocumented operationally, so on-call has no guidance for recovering after an RPC outage or replaying missed ledgers.

Acceptance criteria

• Document how to read indexer lag from /health and /v1/admin/metrics and what lag thresholds mean
• Document the reset vs replay endpoints, when to use each, and that replay is idempotent via the dedup constraint
• Document the INDEXER_*/SOROBAN_RPC_URL/STREAM_CONTRACT_ID env vars and the disabled-indexer behavior

Files to touch

• backend/docs/SSE_ARCHITECTURE.md
• backend/SSE_README.md

Out of scope

• Re-documenting the on-chain data-flow already in ARCHITECTURE.md

[habnark]

@habnark has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

hello can i work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @habnark to this issue.

[femiolutayo]

@femiolutayo has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello Maintainer. I would love to resolve this issue for you in no time. Please assign to me 🙏🏾😭. Thank you

ℹ️ Repo Maintainers: To accept this application, review their application or assign @femiolutayo to this issue.

[Osifowora]

@Osifowora has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

​Hi maintainer, I would love to work on this issue. I can get started on it right away.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Osifowora to this issue.

[Jenola344]

@Jenola344 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer, I will love to work on this

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Jenola344 to this issue.

[Rampop01]

@Rampop01 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I would like to work on this issue . I understand the assignment and the requirements, and I’m confident in the approach needed to deliver the best solution. Kindly assign this task to me.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Rampop01 to this issue.

[Caneryy]

@Caneryy has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi, I'd like to work on this issue please.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Caneryy to this issue.

[grantfox-oss]

🦊 GrantFox — @Rampop01 has been assigned to this issue!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #849)
2. Your PR will be reviewed by the LabsCrypt maintainers

Good luck! Track your progress on GrantFox.

[drips-wave]

Congratulations, @Rampop01! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Rampop01: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊