Instafest is a festival poster creation platform that utilizes Next.js and Vercel to rapidly scale its user base from 100-150 users per hour on the first day to 500,000 new users per hour within days. Anshay Saboo, the creator of Instafest, leveraged Vercel's features such as Functions, Monitoring, and Analytics to handle the enormous traffic and maintain high performance. By utilizing Next.js for its high-performance React sites, Vercel for easy deployment and global Edge Network caching, and built-in optimization features, Instafest was able to achieve viral growth, serving over 100 million page views in a week and peaking at 6 million users per day without downtime or latency issues.