LoopBack VS nest-content-negotiation

Backend is usually an API you design, can simply use Rails for this, basic Express.js or some framework like https://loopback.io/ if you want javascript otherwise you want 'system design' https://github.com/donnemartin/system-design-primer for all the load balancers/dbms if that's what you mean.

LoopBack – Highly Extensible Node.js and TypeScript framework

We deliberately decided not to use "kitchen-sink included" frameworks such as Laravel, Django, Loopback or Nest.js to keep things simple.

Loopback

I'd say check out https://loopback.io

This interface defines the basic CRUD capabilities that any entity should provide. This contract is based on frameworks like Loopback, Django RF, RoR and Spring. The Service.kt looks something like:

Then you have the enhancers, which are really just specialized middleware that can be transport agnostic. You have guards which handle your authentication. If a guard's canActivate returns true (sync or async, promise or observable) then the request continues on. If false is returned, Nest will automatically send back a 403 (customizable through a filter). You have pipes which are for you payload/parameter validation and transformation. Out of the box, Nest support class-validator and class-transformer, but you can use any validation method you prefer (via passing the schema to a custom pipe's constructor) or you can make your own version of the ValidatioinPipe to work with other class based systems like @deepkit/type (I'm slowly working on building this to be a drop in replacement). Next up you have interceptors which are pretty much your swiss-army-knife enhancer. They have pre and post controller logic available so they're great for logging and caching responses, as well as response mapping and serialization (just to name a few things they can do). You can also set up some sweet content negotiation or dynamic template rendering with a bit of clever work. And then you have filters which are your built in error handlers. You throw an error, these can catch it.