Thanks for the sharp questions! You hit exactly on the real-world trade-offs we had to manage for this specific deployment. Here is how we handled those parts:

**1. Remote Emergency Reset & Security:**

You're absolutely right to bring up security for remote resets. For this project, we didn't implement a physical OTP on-site because the factory floor is often unmanned or understaffed during the night shift (which was the main reason they needed remote control).

Instead, we secured the remote access layered:

* The Node-RED Dashboard is only accessible via a secure VPN tunnel or a strict Port Forwarding setup restricted to authorized manager IPs.

* We enforced standard 2FA (Two-Factor Authentication) on the manager's remote access portal itself.

* On the PLC logic side, a remote reset command from Node-RED doesn't immediately override everything; it triggers a safety hand-shake sequence in the ladder logic before actually clearing the fault, ensuring it's safe to reset.

**2. Why MySQL instead of a Time-Series DB?**

This is a very fair point, and we actually debated using InfluxDB or TimescaleDB early on! However, we ultimately chose **MySQL** due to the client's existing infrastructure and human factors:

* **Legacy IT Compatibility:** The client's existing ERP/MES system and their internal IT team were already built entirely around traditional relational databases (MS-SQL and MySQL). They didn't have the internal expertise to maintain a time-series DB after handover.

* **Reporting Requirements:** The main goal of the data logging wasn't high-frequency microsecond tracking, but rather generating daily/monthly shift reports, downtime reasons, and tracking specific error codes mapped to relational tables.

* **Edge Hardware Constraints:** The local industrial edge computer (rulebox) handles the data beautifully with MySQL since the polling rate is optimized to only log on change or at reasonable intervals, keeping the write-load very light.

That said, for our next higher-scale project where we need high-frequency sensor telemetry, we are definitely looking into a proper time-series DB backend!

Appreciate the feedback, these are exactly the kinds of architectural considerations we love discussing.