(At the time this ThoughtWorks Radar was written, XTDB was still known by its previous name, "Crux".)
The Radar is an "opinionated guide to technology frontiers" that tracks a variety of emerging and disruptive Techniques, Tools, Platforms and Languages & Frameworks. The team behind the Radar are careful to point out that it is primarily a view of what they think is interesting rather than a comprehensive market analysis.
XTDB has been classified under the "Assess" ring in the Platform quadrant in this edition, currently alongside the likes of FoundationDB, Delta Lake and Snowflake. The general recommendation for technology in this ring is to keep an eye on it and consider a trial if there is a particularly good fit for your use-cases. Fortunately for XTDB it seems likely that every organisation will have a bitemporal data problem in the future!
The main point of caution listed in the description for XTDB is that it currently lacks SQL query support and only provides Datalog queries. We recognise that not every organisation is able to redirect development resources to embrace the full benefits of Datalog and consequently we are considering adding a SQL query interface in the future. One option available to us for building up an SQL layer on top of Datalog is Apache Calcite.
What do you think of the Radar? Are you looking for SQL queries? Say hello: