Amazon web services – AWS load balancer not running the latest image

I’ve setup an application load balancer with a simple "Hello World" greeting that was built on a Dockerfile.

FROM node:16-alpine
WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install
COPY ./src .
EXPOSE 3000
CMD [ "node", "app.js" ]

My buildspec.yaml to push this image to AWS ECR repo is below

version: 0.2
phases:
  install:
    runtime-versions:
      nodejs: 18
    commands:
      - apt-get update
      - apt-get install -y nginx
  pre_build:
    commands:
      - echo Logging in to Amazon ECR...
      - aws --version
  build:
    commands:
      - aws ecr get-login-password --region $AWS_DEFAULT_REGION | docker login --username AWS 
      -- password-stdin 1234567.dkr.ecr.us-east-1.amazonaws.com
      - docker image build -t 1234567.dkr.ecr.us-east-1.amazonaws.com/demo-ecs-poc-ui .
      - docker push 1234567.dkr.ecr.us-east-1.amazonaws.com/demo-ecs-poc-ui

My app.js file in /src folder is:

var express = require('express');
var app = express();
app.get('/', function (req, res) {
res.send('Hello World!');
});
app.listen(3000, function () {
console.log('Example app listening on port 3000!');
});

This works fine when I visit the load balancer DNS.

Now I changed this and added few react components and my Dockerfile looks like this now.

FROM node:lts-alpine
WORKDIR /app
ENV PATH /app/node_modules/.bin:$PATH
# Copy public directory to /app
COPY public/ /app/public
# Copy src directory to /app
COPY src/ /app/src
COPY package*.json .
RUN npm install
RUN npm i react-scripts
EXPOSE 3000
CMD ["npm", "start"]

There is no change to the buildspec.yaml and I am using the same image.

When I used this Dockerfile, the new image(with react stuff) is pushed successfully to ECR, but when I visit the ALB DNS, it still uses the old image and prints that "Hello World!" instead of the react stuff I put in.

Is there any change I need to make to make my ALB point to the latest image in the ECR repo?
I thought it will always pick up the latest image from the ECR and serve that, probably I am wrong.

I am using 2 different pipeline stacks (one for creating aws resources and the other one for application where the Docker stuff comes into play).

Sorry not a Docker expert, any help is much appreciated.