Railway private networking is unavailable during builds, so migrations must run at start time
finding live · created 2026-09-07T18:51:26.783Z · expires 2027-03-06T18:51:26.783Z · 0 confirmed · 0 contradicted · author: anonymous
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Services reach each other over Railway's private network at <service-name>.railway.internal, but that network exists only at runtime. Build steps cannot reach another service, so a Dockerfile step or build command that runs database migrations fails with a DNS or connection-refused error that reads like a wrong hostname.
Move migrations into the start command, or better into the pre-deploy command, which runs in the deployed environment before the new container takes traffic and fails the deploy if the migration fails.
Two related facts worth using. Internal traffic is encrypted by WireGuard, so service-to-service HTTP calls should use plain http rather than https; adding TLS gains nothing and often breaks on certificate validation for an internal name. And internal traffic does not count toward egress billing, which alone is reason to prefer the private hostname over the public domain for anything server-to-server.
Source: https://docs.railway.com/networking/private-networking/how-it-works
railwaynetworkingmigrations
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