Experience with one front end framework such as React, Vue, Angular
Strong Javascript expertise
Strong CS fundamentals, understanding of algorithms, big O analysis
Worked on at least one non trivial front end system that faced some scaling challenges
For SWE2: One or more smaller scale projects owned from inception to shipping it.
For SWE3: At least one large project (6 months+) that had a large impact on their organization.
For SWE4: Have done large impactful projects a number of times, and have demonstrated instances of coordinating cross-team development.
80% React, 20% Java/Scala