check retention

README.md

@@ -42,6 +42,21 @@ docker run -p 8080:8080 -v $(pwd)/data:/app/data myapp:test
 
 Add services from the dashboard (e.g. `https://example.com`, `google.com:443` for TCP) and view reports.
 
+### Check Retention
+
+To limit database growth, the app prunes old checks every 15 minutes:
+
+| Env var | Default | Description |
+|---------|---------|-------------|
+| `CHECK_RETENTION_COUNT` | 5000 | Keep last N checks per service |
+| `CHECK_RETENTION_DAYS` | 0 (disabled) | Also delete checks older than N days |
+
+Example: keep 2000 checks per service and drop anything older than 30 days:
+
+```bash
+docker run -e CHECK_RETENTION_COUNT=2000 -e CHECK_RETENTION_DAYS=30 ...
+```
+
 ## Jenkins Pipeline
 
 The pipeline: