Thundra can maintain a higher number of concurrent functions (default is 8).

The cold start part is offered free of charge and is part of the basic account functionality (which itself is free of charge).

The system is launched via CloudFormation ans then each function can be tweaked to maintain a specific amount of functions up and running.

https://apm.docs.thundra.io/performance/dealing-with-cold-starts

PS: I’m in no way affiliated with Thundra nor plan to be