To be clear - Cassandra is great for time series but it's not a "time series database" - it just solves all of the same problems (and then some), because it gives you natural replication, real HA, cross-wan, let's you cluster/order data on disk using big table like sorting, and scales over a thousand nodes per cluster.

For sensor data collection, it's very hard to beat. Lay something like spark or filodb on top for more flexibility and it's virtually unmatched.