It is a lot, when we need to scale by adding more Mesos tasks. Every task launches a new JVM instance, which adds to the total memory usage. Also by using a GC and not wanting to collect all the time, you need to add more memory overhead, which is not required with Rust.

Comparison: I have one app written with Scala and consuming 350 megabytes per Mesos task. The similar-sized Rust app is using 8-10 megabytes of RAM. When you have 1000 instances running during a peak, this escalates fast.