Interviewers at Grass will primarily assess candidates' technical proficiency in Rust, their ability to handle backend development tasks, and their experience with tools like Node.js, Redis, Kubernetes, and AWS to ensure they can build, test, and debug high-performance services. They will look for evidence of strong problem-solving skills, attention to detail in code quality, and collaborative experience, as the role involves working with cross-functional teams. Key assessment points include evaluating candidates' familiarity with distributed systems and microservices architecture, their hands-on experience with optimization techniques, and their proficiency in CI/CD and DevOps practices to gauge their readiness for senior-level contributions.