I have two NodeJs Express applications linked to two different database, for convenience let’s call the first application A and the second B, both are linked to the same redis instance with Ioredis.

A can’t access directly B database, it needs to do an HTTP request in order to get data from B database.

In an application A endpoint, I need to check a value from application B database, it is a really high traffic endpoint with hundreds of requests per minutes, I can’t simply do an http request to get data from application B, the performance loss will be too high.

A solution that I found is redis Pub/Sub, I can register from two channels in application A and B.

If the required value is not present in redis i’ll use two channels :

One channel to send messages from application A channel to application B in order to persist objects from database into redis.

A second channel to send messages from application B to application A in order to persist and return the object that was fetch from database.

My question is, is there a way in the application A first channel call to await a return response from application B through the second channel ?

Can something like this work ?

Basic POC

  async function main() {

    await redis.subscribe("get-company", (err, count) => {
      if (err) console.error(err.message);
    });

  
    redis.on("message", (channel, message) => {
      console.log(`Received first message from ${channel} channel.`);
      redis.publish('send-company', 'test')
      console.log(message);
    });
    main2()
  }

  async function main2() {
    await redis2.subscribe("get-company", (err, count) => {
      if (err) console.error(err.message);
    });

    redis2.publish('get-company', 'test').then(async (data)=>{
      console.log('first send completed');
      redis2.on("message", (channel, message) => {
        console.log(`Received response from ${channel} channel.`);
        console.log(message);
        redis2.unsubscribe();
      })
    })
  }

main()