Familiar with upcoming web technologies (e.g., ES6, ES7, Web Components)
Experience with standard front-end development tools such as Babel, Webpack, NPM, etc.
Experience with monitoring, distributed logging and metrics, setting up configuring and analyzing to spot problems (Prometheus, Grafana, Filebeat, Logstash)
Really have that "monitor everything and anything" mentality, from an alerting as well as a metrics point of view