Magento is one of the best eCommerce CMS systems available today. Based on numerous IT technologies, it has a flexible modular architecture and an agile ecosystem that can be continually adapted, customized, and extended for an e-commerce website, benefiting from a large variety of embedded features like data catalog management, marketing tools, analytics, SEO engine optimization, reporting, etc. Choosing the right platform is the only first step.
The other, equally important, side of the coin is how to ensure the eCommerce system is constantly available for lots of concurrent users. The answer is in proper system architecture and in the ability to be scalable both vertically and horizontally.