fetch-event-source VS fastify

* `text/event-stream` relies on a modified version of [Azure's fetch-event-source](https://github.com/Azure/fetch-event-source). They handle errors and chunking better than I was. New version has been tested out to 4 billion fragments rendered on a single page with no errors.

The EventSource Web API for handling SSEs (built into most modern browsers) unfortunately supports only GET requests, which was quite limiting when a POST request with larger body JSON data was required. As an alternative, you can use the Fetch API or a ready library like Microsoft’s Fetch Event Source.

Aforementioned limitations are taken care with a specialised SSE client (inspired by the awesome @microsoft/fetch-event-source) and two separate connection modes: the HTTP/1 safe "single connection mode" that uses a single SSE connection for receiving events with separate HTTP requests dictating the behaviour, and the HTTP/2+ "distinct connections mode" that uses distinct SSE connections for each GraphQL operation, accommodating the parameters in the request itself.

For example, Fastify removed the instanceof operatorfrom its codebase because it was causing problems for those developers that rely on jest as a testing framework.

Both are frameworks but NextJs is for Forntend (web app in browser that use ReactJs under the hood) and NestJs is for Backend (server app running on a server witch use Express or Fastify). The only thing similar between them is the typed language in which they were written.

Restify & Fastify Hapi

Let's create a sample Node API project we can work with throughout to build a new docker image. We will leverage Fastify to create an API that we configure via the fastify-cli.

Fastify

In setting out to build this service, we wanted to use gRPC for its APIs. We’ve been reaching for REST when building APIs so far, primarily out of necessity, i.e., our public APIs needed auto-generated client SDKs and docs for developers working with them. We built those APIs with Fastify and Typebox but felt burned by a code-first approach to generating an OpenAPI spec. I’ll spare you the details and save that experience/learning for another article. Suffice it to say we love gRPC’s schema-first approach. This blog post summarizes our feelings well

Fastify – Fast and Low overhead web framework

Custom Functions are powered by Fastify (a light-weight Node.js framework that claims to be faster than Express.js), so they’re extremely flexible.