I believe that if https://issues.apache.org/jira/browse/KAFKA-16237 got actually pushed forward then the usage of Scala might grow back up again, so I'm not sure if deprecation or discontinuation of Scala support is really the best way to go.
3.5% of developers using 2.13 artifact indicates somewhat interest in using Scala for new or recent projects. On Fri, 24 Oct 2025 at 00:00, Matthias J. Sax <[email protected]> wrote: > I had a look into download numbers (unique IPs), and we have three > artifacts: > > - kafka-streams-scala_2.11: only for older version (2.4 or older); > basically not used any longer > > - kafka-streams-scala_2.12: supported up to 3.9; about 1.2% or KS > developers us it > > - kafka-streams-scala_2.13: about 3.5% or KS developers use it > > So we have combined about 5% of KS developer using Scala. This is many > thousand of developers. > > There is also a ticket about adding Scala 3 support: > https://issues.apache.org/jira/browse/KAFKA-16237 > > > So I would say, overall there is fair usage of this module, so I am not > sure if we would really want to discontinue it? > > If we really want to consider to discontinue the kafka-streams-scala > module, we might want to reach out to the user mailing list, too? > > > > For the process, I agree with Ismael that we could deprecate it with a > KIP, but only remove with AK 5.0 release. > > > -Matthias > > > On 10/23/25 9:15 AM, Ismael Juma wrote: > > Hi Chia-Ping, > > > > There are two places where we use Scala today: `core` (server) and > > `streams-scala` (client library). Eliminating Scala from the former is an > > internal change and is indeed the plan. Deprecating/removing the latter > > requires a KIP since it is a client library with a public API. It's > worth a > > discussion. Input from folks focused on Kafka Streams would be helpful. > > > > Ismael > > > > On Thu, Oct 23, 2025 at 2:33 AM Chia-Ping Tsai <[email protected]> > wrote: > > > >> hi all, > >> > >> While reviewing https://github.com/apache/kafka/pull/20736, I noticed > that > >> streams-scala does not use Scoverage. Given the plan to eventually drop > >> Scala support entirely, I'm questioning whether improving Scoverage for > the > >> streams-scala module is worthwhile, since that module would be included > in > >> the deprecation. Am I correct in this assessment? > >> Best, > >> Chia-Ping > >> > > > >
