PHP. It was what I used initially so I could have access to our internal libs since our main application is in PHP. After crashing the ETL server a couple tim

PHP. It was what I used initially so I could have access to our internal libs since our main application is in PHP. After crashing the ETL server a couple times though, I decided to try moving the heavy lifting to Go. When we benchmarked them, what would take PHP 30 minutes, Go could do in less than 30 seconds. Only the transform is written in Go, the rest of the ETL is still in PHP.