The startup that I work at had started as a project a contracting company had taken on, and they had chosen Java Spring Boot to handle their REST API backend back in 2020.
Although probably not the decision I would have made, it's actually a pretty nice ecosystem that has scaled really well and been fairly easy to work with. Java 21 has _most_ of the QoL features that I like (I'd still really like a `?.` null operator that I can chain together) as well as the ability to reach for JPQL/SQL easily with JpaRepositories when performance is needed.
It's been fairly easy to onboard devs to the project even if they have not had previous experience with Java, and has maintained relatively decent code quality over the last 4 years.
I'm currently working on a LLM project for them that is being completed in Python, however, due to most of the tools being python-first and most of the LLM talent being python-first.
Kotlin would have definitely been a step up over Java purely for null safety.
In hindsight, RoR or Django would probably have been a better starting place considering their financial constraints (non-technical bootstrapping founders), but now that they are larger and more established Spring Boot seems a great framework given their current situation (the originally contracting code needed a major re-write anyway so I'm not sure that would have actually costed more time to go from RoR/Django -> Spring Boot)
Although probably not the decision I would have made, it's actually a pretty nice ecosystem that has scaled really well and been fairly easy to work with. Java 21 has _most_ of the QoL features that I like (I'd still really like a `?.` null operator that I can chain together) as well as the ability to reach for JPQL/SQL easily with JpaRepositories when performance is needed.
It's been fairly easy to onboard devs to the project even if they have not had previous experience with Java, and has maintained relatively decent code quality over the last 4 years.
I'm currently working on a LLM project for them that is being completed in Python, however, due to most of the tools being python-first and most of the LLM talent being python-first.