[avifreedman]

Sorry to keep being pedantic, but I think it's important to thinking about approaches to scalable and performant TSDBs, and I still disagree :)

Your example re: Cassandra is a problem with a particular example of columnar based time series database, not inherently with using columnar-store based backends for time series data.

At Kentik, our in-house backend deals with 80+ columns wide (what would be tags in TSDB) for primarily network data, and querying across tens of billions of records (tens of devices of data for 90 days) usually takes .5-2 seconds.

That's deployed on ~7 backend data nodes, running heavily multi-tenant with 300k-2m records/second ingested and averaging 450 queries/minute across a week (don't have a peak query # handy).

But there's also nothing that says that a columnar store database can't have indexes per column built-in (vs. external).