For example, double delta compression, or Gorilla for floating point numbers. For more, take a look at our open source VictoriaMetrics database, which uses all of such tricks.
- Availability preferred over consistency (you want your metrics when bad things are happening, even if they may not be 100% accurate)
- Extremely write heavy, with most data never being read (they mentioned that only 2% of data is ever read. in my experience at another large company, it was way less than 2%)
- For the data that is read, most of reads are for most recent points (mostly alarms, but some dashboards as well)
- Different SLAs for queries based on usage - ie. queries for alarms must be fast. Dashboards, and trend analysis - not so much.
If I didn't want to use MySQL or Postgres, I'd rank Prometheus #1 and Clickhouse #2.
The killer thing for Clickhouse is that Percona supports it, so if you want to outsource the installation, mgmt. and support, you can just write a check and get good results.
Also, Clickhouse is a column store with SQL, so you could use an instance for monitoring and another to replace Vertica or Greenplum or whatever so long as it has the client libraries you need.
I'm concerned with there being a support issue, as well as a smaller user base also affecting support in the long term.