QA engineers are involved in each phase of the software development lifecycle (SDLC) to improve quality and identify issues early. The six phases are planning, design, implementation, testing, deployment, and maintenance. In planning, QA engineers can identify potential bugs in new features. In design, they can find problems with the design that could cause bugs. During implementation, QA highlights potential user experience issues. Testing involves writing test cases and bug reports. For deployment, QA conducts smoke testing after release. Maintenance is an ongoing process where QA works to prevent bugs from being released.