[nevon]

I realize you're asking about performance optimizations, but since you put it in the context of a workload's cloud bill being too large, I'll chip in and say that by far the largest impact on cost I've seen over the years is to just rightsize the infrastructure the workloads are running on. What I see more than anything is applications that are reserving 10x more CPU or memory than they're actually using. In some cases this might mean amortizing resource usage over time, by asynchronously consuming some kind of queue, in cases where the extreme reservation of resources is due to some temporary usage spike (downstream client doing some batch processing, for example).