Thanks for your help, @danielkec! I tried these optimizations and found the startup time to be around 34 ms.

(28 + 36 + 36 + 36 + 34) / 5 = 34

When I tested Helidon last night, it was 43.8 ms.

I also tested memory:

Megabytes before request: 57 MB (was 74)
Megabytes after request: 81 MB (was 91)
Megabytes after 5 requests: 115 MB (was 124)

Helidon seems to increase the memory used 6-8 MB for each request. Is this a known issue?

Micronaut had a similar problem last year. They added the following to their default application.yml to fix it:

netty.default.allocator.max-order: 3