Show HN: Spring Boot microservice with graphql and mongodb

I recently made a spring boot microservice[0] to query on HN stories in a customized way. It was based on MySQL. How much time/effort do you think it would take someone to migrate to graphql? Also, is what is the speed of a query in graphql? Any pros or cons? Currently I haven't applied any pagination techniques thus it takes much longer to query over 2.2M records. I am trying to get the queries sped up.

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[0] https://news.ycombinator.com/item?id=16560413