geomesa VS geometry-api-java

you could help dockerizing geomesa with/on Cassandra https://www.geomesa.org/ Currently its only dockerized with accumulo

If you really need to scale beyond what Postgres/PostGIS can handle, then you might want to check out GeoMesa[1], which is (very loosely) "PostGIS for HBase, Cassandra, or Google BigTable".

That being said, you may not need it, because Postgres/PostGIS can scale vertically to handle larger datasets than most people realize. I recommend loading your intended data (or your best simulation of it) into a Postgres instance running on one of the extremely large VMs available on your cloud provider, and running a load test with a distribution of the queries you'd expect. Assuming the deliberately over-provisioned instance is able to handle the queries, you can then run some experiments to "right-size" the instance to find the right balance of compute, memory, SSD, etc. If it can handle the queries but not at the QPS you need, then read replicas may also be a good solution.

[1] https://github.com/locationtech/geomesa

I programmed with graphical interface in the past in Java, too, which is definitely one of the top choices for me cause it gives the code a lot of structure and makes it easier to maintain and on top of that there exists a lot of community run libraries that might serve my purpose, like this one. I mostly have experience in designing games (SuperMario, Space Invaders and similar) with Java.

It's good software (I've used it more than a decade), however I found GEOS to be a sticking point. When using it on very large polygons, e.g. 10k to 1 million vertices, memory leaks are not uncommon and performance drops off considerably. Debugging SQL -> C -> C++ is not fun and hacking C++ geometry code when it's not part of your normal work is nigh on impossible. I've found the ESRI geometry API for Java to be by far the best geometry API out there. Harder to use initially and obviously JVM specific but faster and more reliable. It's a very good fit for Hadoop / Spark or other JVM applications. Ignore the brand name, I'm not affiliated and it's FOSS with an Apache license.

https://github.com/Esri/geometry-api-java