Run a second copy of your app and things break quietly. The cron job runs twice. The rate limit lets through twice the traffic. One replica keeps calling a dead service the other already gave up on.

grelmicro fixes that with one line that says where shared state lives: Redis, Valkey, PostgreSQL or SQLite. Works with FastAPI, Starlette, Litestar and FastStream. Python 3.14+.

pip install "grelmicro[fastapi,redis]"

Documentation: https://grelmicro.grel.info/

Source Code: https://github.com/grelinfo/grelmicro

Start with one pattern

Run a job once a minute across all your replicas, not once per replica. Create a file main.py with:

from fastapi import FastAPI

from grelmicro import Grelmicro
from grelmicro.providers.redis import RedisProvider
from grelmicro.task import Tasks

app = FastAPI()
tasks = Tasks()
micro = Grelmicro(uses=[RedisProvider("redis://localhost:6379/0"), tasks])
micro.install(app)

@tasks.every(interval=60,…