Run mongodb in memory on Docker without using TMPFS (https://github.com/docker-library/mongo/issues/224)

db.mjs

import { MongoMemoryServer } from 'mongodb-memory-server';

// This will create an new instance of "MongoMemoryServer" and automatically start it
const mongod = await MongoMemoryServer.create({
  instance: {
    port: 27017,
    ip: "::,0.0.0.0",
    dbName: 'in_memory'
  }
});

const uri = mongod.getUri();
console.log("Running in-memory MongoDB on " + uri);

Dockerfile

FROM node:16
RUN apt-get install libcurl4

WORKDIR /project
COPY ./db.mjs /project

RUN yarn add mongodb-memory-server
ENTRYPOINT ["node", "./in-memory-db.mjs"]