Every CollatrEdge installation has a local SQLite store. Always on. Not optional.
This is the thing that most IIoT platforms get wrong. They treat local storage as a fallback. Something that kicks in when the cloud connection drops. An afterthought.
For most UK manufacturers, local storage is the primary mode. The data stays on site. It gets queried on site. It gets exported as CSV from a browser on the factory network. The cloud connection, if it exists at all, is secondary.
The store-and-forward buffer is separate from the local store. It holds data destined for remote outputs when those outputs are temporarily unavailable. When the connection comes back, it drains. Oldest first.
SQLite handles both. WAL mode for concurrent reads and writes. Daily file rotation for manageable backups. Integrity checks on startup to recover from power loss.
We tested power loss recovery explicitly. Corrupt WAL files. Truncated databases. The agent recovers and keeps running. Because the power does go out in factories. More often than you would think.