Scala
JVM language that blends functional + OO. Martin Odersky, EPFL, 2004. Influential type system design. Big city: Twitter, LinkedIn, Netflix run Scala-heavy stacks.
Scala 3 (2021) total redesign — new syntax (indentation-based), better type system. Akka (actors), Spark, Kafka are written in Scala. Lightbend (formerly Typesafe) is the commercial company. The Akka license change (BSL, 2022) was controversial. Competitor: Kotlin (more pragmatic, chasing Java directly). Scala jobs declined since ~2020 but the language has devoted followers.