Can I use model which is trained using Keras to Scala?
Yep, check this blog: https://towardsdatascience.com/deploying-keras-deep-learning-models-with-java-62d80464f34a

Dump your model as .h5 like you normally would and load it in java using those libs from blog.

Another idea would be to create separate AI microservice in python(django/flask). That's what I usually do.