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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
Another option is https://github.com/SciSharp/Pandas.NET but it looks also as a toy project without examples/tutorials.
CsvHelper should work fine with all those constraints. It's pretty much the standard for working with CSVs in .Net. AFAIK it doesn't care about column order (there might be options to tell it about column order) or extra columns. If the column names are known at compile time then it's super easy to use. If they aren't known until runtime then it'll be more work but you can dynamically build a ClassMap describe the current document.