Add Prometheus /metrics endpoint

[Miracle656]

Background

Lens runs continuously ingesting trades and serving prices, but exposes no operational metrics. When ingestion stalls or prices stop updating, there is no automated way to detect it. A Prometheus /metrics endpoint enables dashboards and alerts on key ingestion and API health signals.

Key metrics to expose

• trades_ingested_total — counter per pair
• amm_snapshots_total — counter per pool
• price_requests_total — counter
• x402_payments_received_total — counter
• last_trade_timestamp — gauge per pair
• db_query_duration_seconds — histogram

Key files

• src/metrics.ts — create using prom-client
• src/server.ts — register GET /metrics
• src/ingesters/ — increment counters

Suggested execution

git checkout -b feat/prometheus-metrics

1. npm install prom-client
2. Create src/metrics.ts with all metrics defined above
3. Instrument both ingesters and the x402 middleware
4. Add GET /metrics returning Prometheus text format with no x402 gate

Example commit message:
feat(api): add Prometheus /metrics endpoint with ingestion and payment counters

Acceptance criteria

• GET /metrics returns valid Prometheus text
• At least 5 custom metrics
• No x402 gate on the metrics endpoint

---

Drips Wave · Complexity: Medium · 150 points
Comment below to request assignment. PR must include Closes #[this issue].

[K1NGD4VID]

@K1NGD4VID has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Hi!
Please, assign me this issue. I’ve worked on similar Prometheus instrumentation before, so I can implement the /metrics endpoint, define and expose the required counters/gauges, and integrate them across ingesters and middleware with proper formatting. ETA: 3–4 hours

ℹ️ Repo Maintainers: To accept this application, review their application or assign @K1NGD4VID to this issue.

[drips-wave]

Congratulations, @K1NGD4VID! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

🧑‍💻 @K1NGD4VID: 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 🌊