I think next step could be to use Koa but I am not sure.
What does Koa offer to your team that Express does not?
I heard Koa could have best performance. I'd need to try.
Have a look at https://www.fastify.io/ as well.
Hi, I have written an article related to KOA which can help all of you for learning purpose. Find it here: https://blog.carbonteq.com/what-is-koa-a-brief-overview/