Create a good k6 load test with graphql/subscription

Question

After struggling against k6, with the help of the answers to my other question, i was able (i think) to test subscriptions with websocket.

Now i'm trying to desing a good test. Our app is a Single Page App that mainly uses websocket subscriptions instead of queries. The problem is that i'm a bit lost on how to define how many subscriptiosn i should test in order to detect if my app will be able to support around 800 users working simultaneously in real time. (I started testing it first with a top of 150 VUs).

For now, i'm running the test with 3 commonly used subscriptions in our user path, but:

1. Should I try more subscriptions, trying to cover the most used ones in our user path, or should I keep it simple and pick the 3 most used ones and add a timeout between them?

2. Is this a correct approach for load/stress testing with GRAPHQL subscriptions/websocket? I'm not sure if i'm being too cautious about this, but i'm afraid of giving a false status about our situation.

3. I am a bit confused on how to interpret the results screen, especially on how I can infer if we will be able to give a good experience to our users. Should I take the avg and p(95) of ws_ping as a reference for this?

k6 screen result

As a reference, here is part of the code i'm using to perform the test

Thanks in advance!

main.js

import { Httpx } from 'https://jslib.k6.io/httpx/0.0.5/index.js';

const session = new Httpx({
  baseURL: `https://${enviorment}`
});

const wsUri = `wss://${enviorment}/v1/graphql`;

const pauseMin = 2;
const pauseMax = 6;

export const options = {
  stages: [
    { duration: '30s', target: 50 },
    { duration: '30s', target: 100 },
    { duration: '30s', target: 150 },
    { duration: '120s', target: 150 },
    { duration: '60s', target: 50 },
    { duration: '30s', target: 0 },
  ]
};

export default function () {
  session.addHeader('Content-Type', 'application/json');
  todas(keys.profesorFirebaseKey, keys.desafioCursoKey, keys.nivelCurso, keys.profesorKey)
}

todas.js:

import ws from 'k6/ws';
import {fail,check} from 'k6'
import exec from 'k6/execution';

export function todas(id, desafioCursoKey, nivel, profesorKey) {

  const queryList = [`];

  let ArraySubscribePayload = []

  for (let i = 0; i < 3; i++) {
    let subscribePayload = {
      id: String(1 + 3 * i),
      payload: {
        extensions: {},
        query: queryList[i],
        variables: {},
      },
      type: "start",
    }
    ArraySubscribePayload.push(subscribePayload)
  }

  const initPayload = {
    payload: {
      headers: {
        xxxxxxxxxxxxx
      },
      lazy: true,
    },
    type: "connection_init",
  };

  const res = ws.connect(wsUri, initPayload, function (socket) {

    socket.on('open', function () {

      socket.setInterval(function timeout() {

        socket.send(JSON.stringify(initPayload));

        socket.send(JSON.stringify(ArraySubscribePayload[0]));

        socket.setTimeout(function timeout() {
         
          socket.send(JSON.stringify(ArraySubscribePayload[1]));
          socket.send(JSON.stringify(ArraySubscribePayload[2]));
          ArraySubscribePayload[1].id = String(parseInt(ArraySubscribePayload[1].id) + 1)
          ArraySubscribePayload[2].id = String(parseInt(ArraySubscribePayload[2].id) + 1)
        }, 3000);

        ArraySubscribePayload[0].id = String(parseInt(ArraySubscribePayload[0].id) + 1)
        socket.ping();
      }, 7000);
    })
  });
}