"""Synthetic local application example. No network or database calls."""
import json
now=100; window=10
observations={"S1":95,"S2":70}
result=[]
for id in ["S1","S2","S3"]:
    seen=observations.get(id)
    state="no_observation" if seen is None else "current" if now-seen<=window else "stale"
    result.append({"id":id,"observed_minute":seen,"freshness":state})
assert [r["freshness"] for r in result] == ["current","stale","no_observation"]

print(json.dumps(result, indent=2, ensure_ascii=False))