Deploying Google App Engine Nest.js via Bitbucket Pipelines - google-app-engine

Question

In my current setup, I use Bitbucket Pipelines to deploy a Nest.js backend to Google App Engine. Unfortunately, I haven't gotten my NestJS backend up and running yet. Before I had the same setup with a simple Express.js backend which worked without problems.
The problem is as follows and I am now at a loss as to what else to try:
Here's my bitbucket-pipelines.yaml:
image: node:16.15.0
pipelines:
branches:
master:
- step:
name: Install Dependencies & Build Application
script:
- npm install
- npm run build
- step:
name: Deploy to Google App Engine
deployment: development
script:
- pipe: atlassian/google-app-engine-deploy:1.0.0
variables:
KEY_FILE: $KEY_FILE
PROJECT: 'example-project'
VERSION: 'development'
DEPLOYABLES: 'default.yaml'
STOP_PREVIOUS_VERSION: 'true'
Here's my package.json:
{
"name": "example-project",
"version": "0.0.1",
"description": "",
"author": "",
"private": true,
"license": "UNLICENSED",
"scripts": {
"prebuild": "rimraf dist",
"build": "nest build",
"format": "prettier --write \"src/**/*.ts\" \"test/**/*.ts\"",
"start": "NODE_ENV=production node dist/main",
"start:dev": "NODE_ENV=development nest start --watch",
"start:stage": "NODE_ENV=stage nest start --watch",
"start:release": "NODE_ENV=release nest start --watch",
"start:prod": "NODE_ENV=production node dist/main",
"start:debug": "nest start --debug --watch",
"db": "../../cloud_sql_proxy -instances=example-project=tcp:3306",
"lint": "eslint \"{src,apps,libs,test}/**/*.ts\" --fix",
"test": "jest",
"test:watch": "jest --watch",
"test:cov": "jest --coverage",
"test:debug": "node --inspect-brk -r tsconfig-paths/register -r ts-node/register node_modules/.bin/jest --runInBand",
"test:e2e": "jest --config ./test/jest-e2e.json"
},
"dependencies": {
"#hapi/joi": "^17.1.1",
"#nestjs/cli": "^8.0.0",
"#nestjs/common": "^8.0.0",
"#nestjs/config": "^2.0.0",
"#nestjs/core": "^8.0.0",
"#nestjs/mapped-types": "^1.0.1",
"#nestjs/platform-express": "^8.0.0",
"#nestjs/typeorm": "^8.0.3",
"buffer-to-stream": "^1.0.0",
"class-transformer": "^0.5.1",
"class-validator": "^0.13.2",
"cloudinary": "^1.30.0",
"firebase-admin": "^10.2.0",
"module-alias": "^2.2.2",
"mysql": "^2.18.1",
"pg": "^8.7.3",
"portfinder": "^1.0.28",
"reflect-metadata": "^0.1.13",
"rimraf": "^3.0.2",
"rxjs": "^7.2.0",
"typeorm": "^0.2.45",
"typeorm-naming-strategies": "^4.1.0"
},
"devDependencies": {
"#nestjs/schematics": "^8.0.0",
"#nestjs/testing": "^8.0.0",
"#types/express": "^4.17.13",
"#types/hapi__joi": "^17.1.8",
"#types/jest": "27.4.1",
"#types/multer": "^1.4.7",
"#types/node": "^16.0.0",
"#types/supertest": "^2.0.11",
"#typescript-eslint/eslint-plugin": "^5.0.0",
"#typescript-eslint/parser": "^5.0.0",
"eslint": "^8.0.1",
"eslint-config-prettier": "^8.3.0",
"eslint-plugin-prettier": "^4.0.0",
"jest": "^27.2.5",
"prettier": "^2.3.2",
"source-map-support": "^0.5.20",
"supertest": "^6.1.3",
"ts-jest": "^27.0.3",
"ts-loader": "^9.2.3",
"ts-node": "^10.0.0",
"tsconfig-paths": "^3.10.1",
"typescript": "^4.3.5"
},
"jest": {
"moduleFileExtensions": [
"js",
"json",
"ts"
],
"rootDir": "src",
"testRegex": ".*\\.spec\\.ts$",
"transform": {
"^.+\\.(t|j)s$": "ts-jest"
},
"collectCoverageFrom": [
"**/*.(t|j)s"
],
"coverageDirectory": "../coverage",
"testEnvironment": "node"
}
}
Maybe someone has already made experiences with this stack and can help me.