How to add health check and readiness endpoints to FastAPI

Health Check Endpoints

Load balancers and Kubernetes need health endpoints to know when to route traffic to your app. A liveness probe checks if the app is running. A readiness probe checks if it can serve traffic (e.g., database connected).

Basic health endpoint

from fastapi import FastAPI
from sqlalchemy import text
from .database import SessionLocal

app = FastAPI()

@app.get("/health")
def health():
    return {"status": "ok"}

@app.get("/health/ready")
def readiness():
    try:
        db = SessionLocal()
        db.execute(text("SELECT 1"))
        db.close()
        return {"status": "ready", "database": "ok"}
    except Exception as e:
        raise HTTPException(
            status_code=503,
            detail={"status": "not ready", "database": str(e)}
        )

/health always returns 200 if the process is alive — Kubernetes uses this as the liveness probe and restarts the container if it fails. /health/ready returns 503 if the database is unreachable — Kubernetes stops sending traffic to the pod until it recovers.

Keep health endpoints fast. Never run expensive queries in them. The SELECT 1 ping is sufficient to verify connectivity. Add Redis and any other critical dependencies to the readiness check.