turns out cross AZ is recommended for ES. perhaps our data team was rewritting the indices too often. but it was an internal requirement. so I think the data schema could have been more efficient to append deltas instead of reindexing all. but none of that will inflate your bill significantly at Hetzner. of course it will at AWS as that's how they incentivise clients to optimize and reduce their impact. and that's how you cut your runway by 3-6 months in compute heavy startups