Worked on the percona/percona-server-mongodb repository to enhance correctness and reliability in multi-role request handling. Focused on backend development and database internals using C++, the work involved implementing invariant checks to ensure the ServiceEntryPoint consistently uses the correct service context for ShardServer and RouterServer roles. Refactored the OpMsgFuzzerFixture to support separate client strands, which improved test isolation and overall test quality. Added explicit assertions to validate cluster roles at entry points, reducing the risk of edge-case bugs and improving request routing safety. These targeted changes increased confidence in multi-role deployments and strengthened the robustness of request handling logic.