Deploy and Host Prometheus on Railway

Prometheus is the standard open-source monitoring system and time-series database: it scrapes metrics from your services over HTTP, stores them, and answers PromQL queries for dashboards and alerts. Grafana, Alertmanager and most of the cloud-native ecosystem speak to it.

This template runs Prometheus 3.15 from a thin wrapper around the official image: the Prometheus web UI and API on a Railway public domain, a Railway volume holding the time-series database, and a generated password in front of all of it.

About Hosting Prometheus

It is behind a login from the first request. Prometheus has no authentication of its own, so the stock image on a public Railway domain hands the query API, the loaded config and every scrape target to anyone with the URL. Here a password is generated per deploy (PROMETHEUS_PASSWORD), turned into a bcrypt web config at boot, and every route, including the API, answers 401 without it. The container refuses to start if the password is missing.
Retention cannot fill your volume. The stock image keeps 15 days with no size limit, and a busy target can fill the disk before the time limit arrives. The entrypoint reads the volume's real size at boot and sets --storage.tsdb.retention.size to 80% of it.
Scrape targets come from variables. Set SCRAPE_TARGETS to a comma-separated list such as api.railway.internal:3000,worker.railway.internal:9100 and redeploy; no config file to edit. For anything more elaborate, put a full prometheus.yml in PROMETHEUS_CONFIG.
Data survives redeploys. The volume at /prometheus is chowned at boot and the database runs as the unprivileged nobody user; samples written before a redeploy were read back after it.
Remote write is on. /api/v1/write accepts pushes from Grafana Alloy, Agent or another Prometheus, behind the same password.

Common Use Cases

Metrics for the other services in your Railway project, scraped over the private network
A data source for Grafana dashboards (use PROMETHEUS_PRIVATE_URL with basic auth)
Alerting rules and long-lived service-level numbers for an app or a fleet of apps
A remote-write target for agents that push metrics from outside Railway

Dependencies for Prometheus Hosting

One Railway volume for the time-series database (created by the template)

Deployment Dependencies

Prometheus documentation: https://prometheus.io/docs
Basic auth in Prometheus: https://prometheus.io/docs/guides/basic-auth/
Official image: https://hub.docker.com/r/prom/prometheus
Wrapper source: https://github.com/bon5co/prometheus-railway

Implementation Details

Variable	Purpose
`PROMETHEUS_PASSWORD`	Password for the web UI, API and remote write, generated per deploy. The user name is `admin` (override with `PROMETHEUS_USER`).
`PROMETHEUS_PRIVATE_URL`	URL on the private network, for Grafana or other services in the project.
`SCRAPE_TARGETS`	Optional. Comma-separated `host:port` list to scrape.
`METRICS_PATH`	Optional. Path on those targets, default `/metrics`.
`RETENTION_TIME`	Optional. Default `15d`.
`RETENTION_SIZE`	Optional. Default 80% of the volume, for example `3GB`.
`PROMETHEUS_CONFIG`	Optional. A complete `prometheus.yml`, replaces the generated one.

The healthcheck is off because every route needs the password; the service restarts on failure.

Why Deploy Prometheus on Railway?

Railway is a singular platform to deploy your infrastructure stack. Railway will host your infrastructure so you don't have to deal with configuration, while allowing you to vertically and horizontally scale it.

By deploying Prometheus on Railway, you are one step closer to supporting a complete full-stack application with minimal burden. Host your servers, databases, AI agents, and more on Railway.