Difference between time-series database and relational database
Time Series Database Advantages:
- Throughout 100K+ to 1M+ inserts per second
- Bytes stored per time/value tuple: 2-10 vs 30-100 (rdbms)
- Built-in time series transformation and aggregations functions
- Schema optimized for time-series arrays with built-in sharding and indexing
Relational Database Advantages:
- Full SQL support
- Ability to store any data other than time-series
- Extensive DBA resources and tooling
By writing your own application code and stored procedures you can accomplish almost everything that TSDBs provide, but you may end up with an implementation that is slower and more demanding in terms of underlying compute and storage resources.
For all practical purposes and with some compromises to referential integrity, you can have both databases run concurrently: store your extended app schema in relational database and time-series in TSDB.