I have 1 common project including both frontend and backend, sometimes backend sometimes frontend is getting new commits but my pipeline yml is working for both of them and deploying both to server even if they have no change. In other words, If I add 1 line of code to frontend, pipeline is deploying backend too. Here is my bitbucket-pipeline.yml

This is an example Starter pipeline configuration

pipelines:
  branches:
    master: 
      - step:
          name: 'Frontend Build'
          image: node:16.4.2
          script:
            - cd myfrontend
            - npm install
      - step:
          name: 'Backend Build and Package'
          image: maven:3.8.3-openjdk-17
          script:
            - cd myfolder
            - mvn clean package
          artifacts:
            - mybackend/target/mybackend-0.0.1-SNAPSHOT.jar
      - step:
          name: 'Deploy artifacts to Droplet'
          deployment: production
          script:
            - pipe: atlassian/scp-deploy:0.3.3
              variables:
                USER: root
                SERVER: 138.138.138.138
                REMOTE_PATH: '/root/artifacts/target/'
                LOCAL_PATH: mybackend/target/mybackend-0.0.1-SNAPSHOT.jar
            - pipe: atlassian/scp-deploy:0.3.3
              variables:
                USER: root
                SERVER: 138.138.138.138
                REMOTE_PATH: '/root/artifacts'
                LOCAL_PATH: mybackend/Dockerfile
            - pipe: atlassian/scp-deploy:0.3.3
              variables:
                USER: root
                SERVER: 138.138.138.138
                REMOTE_PATH: '/root/automation-temp-folder'
                LOCAL_PATH: mybackend/README.MD

In this example the frontend is not deployed but I will activate it. So What I need is that I want to execute a step according to that which folder/project got commit to in it. e.g. If there is a commit under mybackend then only deploy mybackend and if front end.. so on. Is it possible to execute a step for a specific folder ?

Yes, this is achievable by using condition keyword:

This allows steps to be executed only when a condition or rule is satisfied. Currently, the only condition supported is changesets. Use changesets to execute a step only if one of the modified files matches the expression in includePaths.

Your end result should look similar to this:

pipelines:
  branches:
    master: 
      - step:
          name: 'Frontend Build'
          image: node:16.4.2
          script:
            - cd myfrontend
            - npm install
          condition:
              changesets:
                 includePaths:
                   - "myfrontend/**"
      - step:
          name: 'Backend Build and Package'
          image: maven:3.8.3-openjdk-17
          script:
            - cd myfolder
            - mvn clean package
          condition:
              changesets:
                 includePaths:
                   - "myfolder/**"
          artifacts:
            - mybackend/target/mybackend-0.0.1-SNAPSHOT.jar
      - step:
          name: 'Deploy artifacts to Droplet'
          deployment: production
          script:
            - pipe: atlassian/scp-deploy:0.3.3
              variables:
                USER: root
                SERVER: 138.138.138.138
                REMOTE_PATH: '/root/artifacts/target/'
                LOCAL_PATH: mybackend/target/mybackend-0.0.1-SNAPSHOT.jar
            - pipe: atlassian/scp-deploy:0.3.3
              variables:
                USER: root
                SERVER: 138.138.138.138
                REMOTE_PATH: '/root/artifacts'
                LOCAL_PATH: mybackend/Dockerfile
            - pipe: atlassian/scp-deploy:0.3.3
              variables:
                USER: root
                SERVER: 138.138.138.138
                REMOTE_PATH: '/root/automation-temp-folder'
                LOCAL_PATH: mybackend/README.MD
           condition:
              changesets:
                 includePaths:
                   - "myfolder/**"

See here for more details.