Difference between frontend, backend, and middleware in web development

Question

I was wondering if anyone can compare/contrast the differences between frontend, backend, and middleware (\"middle-end\"?) succinctly.

Are there cases where they ove

Answer 1

Here is a real world example which shows front/mid/back end.

General description:

• Frontend is responsible for presenting data to user. Please note interesting quirk that you may have two different front ends associated with single backend
• Backend provides business logic/data persistence.
• Middleware (activemq in the picture) is responsible for system to system. integration between backends. Usually it is installed as separate application

Overlapping:

It is possible to have overlapping between frontend and backend. This usually leaads to long-term issues with application maintenance and scalability. Fairly common in legacy applications.

Most modern technology stacks encourage developers to have strict separation. For example in the picture you can see that backend of the first system has rest web service which is a clear separation line.

Bottlenecks

Most bottlenecks in large are caused by database/network. Databases are located in backend. As for network issues every connection goes through netowrk, so every connection has potential for being slow. With good application design these issues are avoidable to large extend.