Having helped companies like Credit Karma to scale interfaces and double user count. I optimize web apps for speed, cross-browser compatibility, improved SEO rankings and remove bottlenecks. https://rutkat.com
I worked directly with the SEO Manager at Credit Karma to implement code which made search results appear in a desired way on Google. This is important when you have multiple verticals, products and entry points to your website.
Ideas are abundant. It's the execution that counts to validate your idea. You can hire me to show you very affordable ways to test your lean startup or even help you build it. My experience comes from hackathons where I built demos in 48 hours and winning some of them.
Metrics is everything. Verbal feedback from an app user is going to be different than how they actually use the app. Understanding your user's behavior is crucial to your app's success. At Credit Karma, I've worked on their tracking system. I've integrated Zendesk's tickets to web apps which improved customer service. Don't neglect this in your app!