First of all, comparing Flask - a web framework with programming language and a JavaScript runtime. So I will take your question as Flask vs Go and node.js web framework available solutions. Still it depends on your product and it's objectives, is it going to be high loaded or do you prioritize rapid development. in any case, I would not recommend flask, because python is not as good in handling concurrency as go and node.js, the only case i see flask suitable, is when you already know flask and want to develop MVP product ASAP. In other cases, go and node.js is great, both are great at handling high load and thousands of concurrent users, but if we dig in, we discover that go's "bottleneck" is still wider, it is better in handling load, and rapid development with JavaScript is easier, cheaper and more real.