On the surface, the first impression is that a web framework is slow because there is a lot of boiler plate and unnecessary code that is not needed for your application, and that is a valid impression. In practice, slowness is usually not a product of your framework's bloat or the language choice. Slowness is likely a result of the fact that your request is communicating with other services across your network. In our case, these other services are PostgreSQL, Redis, Cassandra, and Memcached, just to name a few. Slow database queries and network latency generally outweigh the performance overhead of a robust framework such as Django.
via NoSQL databases