Concepts docs: Presence, heartbeat & connection liveness

[codebestia]

Write apps/backend/docs/concepts-presence-heartbeat.md explaining services/presence.ts and services/heartbeat.ts — the Redis-backed per-device/per-user presence model, TTL-based liveness, the 30s/90s heartbeat timing, and how multi-device aggregation works.

Acceptance criteria:

• Explains the Redis key structure used for presence tracking (which keys exist, what each holds, TTLs)
• Explains the heartbeat timing contract with the actual current interval/timeout values
• Explains multi-device aggregation and the transition-broadcast behavior

[Samuel-21-eng]

@Samuel-21-eng has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Can I work on this issue

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[drips-wave]

Congratulations, @Samuel-21-eng! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @Samuel-21-eng: 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

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🌊 Happy Wave 🌊

[Confidence001Jewel-cmd]

@Confidence001Jewel-cmd has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Dear Maintainer,
Please assign this issue to me, I will love to work on it.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Confidence001Jewel-cmd to this issue.

[KHALLEY]

@KHALLEY has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi Maintainer, please assign this issue to me. Thank you

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[VictorEzenma]

@VictorEzenma has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi maintainer, I would like to work on this

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

[DrSa7ag3]

@DrSa7ag3 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello, I’ve read through the issue description and understand the expected outcome. I’d be glad to work on it in the next few hours.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @DrSa7ag3 to this issue.

[ChukwuemekaP1]

@ChukwuemekaP1 has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Good day, my name is Chukwuemeka and I'd love to work on this issue.

I have experience with backend development, Redis-backed systems, and technical documentation, so I can approach this from both the implementation and documentation sides. The important part of this issue is documenting the actual liveness model rather than describing a generic presence system.

I'll trace "services/presence.ts" and "services/heartbeat.ts" to document the Redis key structure, stored values, TTL behavior, and the current 30s heartbeat/90s timeout contract. I'll also explain how presence is aggregated across multiple devices and when transition broadcasts are triggered, keeping the documentation aligned with the current implementation.

ETA: 24 hours from assignment. Looking forward to your reply!

ℹ️ Repo Maintainers: To accept this application, review their application or assign @ChukwuemekaP1 to this issue.

[flare-999]

@flare-999 has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

I'm interested on working on this
could you assign this issue to me

ℹ️ Repo Maintainers: To accept this application, review their application or assign @flare-999 to this issue.

[Dannyorji]

@Dannyorji has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

I will like to work on this

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