Nothing wrong with Java as such. The red flag is the "rewriting" part. Assuming that your current server code is running well and meeting all the requirements

Nothing wrong with Java as such. The red flag is the "rewriting" part. Assuming that your current server code is running well and meeting all the requirements, the decision to rewrite has a "smell" and statistically such rewrites are doomed. If there are good reasons for the rewrite and there are competent resources on the project, then perhaps you could consider Scala or Clojure. They allow you to use JVM and gain many other benefits. Check out the respective web sites if you are interesting in championing such an approach. Personally, I would just find another project / company. IMHO Java language is not the issue, it is the multitude of APIs and frameworks and the inherent accidental complexity of it all that trips up projects where suitable experienced team members are not available.