The most time and energy has been getting my head around the source data [0] and industry-specific nuances.

In terms of stack I have a self-hosted Dagster [1] data pipeline that periodically dumps the data onto Cloudflare R2 as parquet files. I then have a self-hosted NodeJS API that uses DuckDB to crunch the raw data and output everything you see on the map.

[0] Mostly from https://bmrs.elexon.co.uk/ [1] https://dagster.io/