Rather than upgrade at this stage, is your system running optimally?
For example see this thread about throttled CPU due to low supply voltage.
Also look at the demands made on the pi, can they be optimised.
I also run numerous iot interactions + Influx + Grafana + Mosquitto etc, and just one such example of optimisation is;
I monitor power used, solar power generated & power diverted from a 5 second feed, and was then running a query to crunch that data to get energy per day (kWh/d). This was done every 5 seconds. That's almost 52,000 individual power/timeframe calculations, which were then added together, every 5 seconds.
Instead, I moved the power/timeframe calculation to node-RED, and converted the feeds realtime to W/s - just 1 calculation per feed per 5 seconds. This was then saved to Influx.
To then get kWh/d, all Grafana needs to do is grab the W/s datapoints for previous 24hrs and simply add them together.
This dropped system demands dramatically, and made a significant difference to the speed at which Grafana presented the dashboards.
