100% Uptime: Every site especially E-commerce portals considered a mission-critical application and does not want to lose business opportunities for even a millisecond of downtime.

No Fixed Schedule for Visitors, they can come anytime.

Robust: Can handle a massive influx of new visitors or traffic. Try the services offered by loader.io, loadimpact.com, and blitz.io or use work, siege, and apache bench to send plenty of virtual traffic to test traffic levels

Caching: Serve pre-generated content to the returning visitors using CDN (Content Delivery Network) and speeds up your site to visitors.

Mobile Experience: More than 50% of visitors are using mobile devices for Internet usage. The site looks great and critical processes are running on tablets, phablets, and smartphones.

Security: The host ensures the safety of your website preventing it from malware infection or compromised personal data. Automatic updations of CMS and themes and plugins for CMS-based software. Not allowing weak passwords.

Highly Optimized communication with databases: Microsoft SQL Server or MySQL allows quick retrieval of information and enables rapid processing of data.

Use Streaming Servers: For audio, video, Shockwave or Flash files use streaming servers.

Dedicated IP: Use SSL and dedicated IP

If Economic barriers are not there, use Dedicated or VPS Hosting, avoid Shared Hosting
Shared Hosting has too many hosts sharing resources.