At some point our cross-AZ traffic for Elasticsearch replication at AWS was more expensive than what we'd pay to host the whole cluster replicated across multiple baremetal Hetzner servers.
Could we have done better with more sensible configs? Was it silly to cluster ES cross-AZ? Maybe. Point is that if you don't police every single detail of your platform at AWS/GCP and the like, their made-up charges will bleed your startup and grease their stock price.
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
Could we have done better with more sensible configs? Was it silly to cluster ES cross-AZ? Maybe. Point is that if you don't police every single detail of your platform at AWS/GCP and the like, their made-up charges will bleed your startup and grease their stock price.