I found out my issue is due to my file structure and I forgot to update my `Dockerfile` to correct path for tutorial 2 (huge blunder).

My file structure

Dockerfile before update:

FROM node:24.5.0

WORKDIR /app

# Wrong path!
COPY ./1-node-js-rest-server/package.json package.json
COPY ./1-node-js-rest-server/package-lock.json package-lock.json

RUN npm install

# Wrong path!
COPY ./1-node-js-rest-server/server.js .

CMD ["node","server.js"]

Dockerfile after update:

FROM node:24.5.0

WORKDIR /app

# Fixed path!
COPY ./2-database-and-compose/package.json package.json
COPY ./2-database-and-compose/package-lock.json package-lock.json

RUN npm install

# Fixed path!
COPY ./2-database-and-compose/server.js .

CMD ["node","server.js"]

After rebuilding my image, now everything works correctly.

Mongodb container data persists as expected, even after I had restarted it.