From 26 Minutes to 20 Seconds: Using pprof to optimize large GraphQL Operations in Go

The open-source GraphQL engine, graphql-go-tools, used by WunderGraph, experienced a significant performance difference when a customer routed a mutation through their gateway built on top of graphql-go-tools. While the mutation took around 1 minute when executed directly against their GraphQL servers, routing it through the gateway resulted in approximately 70 minutes. Investigation revealed that the performance issue was caused by handling a large bulk operation with 70,000 input items, and a workaround was found by moving the data to the variables JSON. By implementing optimizations for JSON encoding and input value injection, the execution time of the operation was drastically reduced from 26 minutes to 150 milliseconds, impressing the customer with a 98.71% improvement. Additionally, using the gateway proved faster than executing the mutation directly against the GraphQL server due to the optimized parser and normalization engine of graphql-go-tools.