A DevOps engineer has developed a CI/CD pipeline for an application comprising five independent AWS Lambda functions. The pipeline, utilizing AWS CodePipeline and AWS CodeBuild, sequentially builds, tests, packages, and deploys each Lambda function. It is triggered by an Amazon EventBridge rule to initiate promptly upon source code changes. However, the engineer has observed that the pipeline's completion time is excessive. What strategy should the engineer adopt to enhance the pipeline's efficiency?