I'm not saying that arena allocators are a bad tool. It seems like a very good fit for your case, where the lifetime of a request is pretty well constrained, an

I'm not saying that arena allocators are a bad tool. It seems like a very good fit for your case, where the lifetime of a request is pretty well constrained, and issues like fragmentation and overallocation won't matter too much. But still I think the OP completely misses the discussions of these aspects.