Number of Users / Sessions / Transactions

I wish it was as easy as giving a number of users or sessions which serve as a threshold to moving to a more powerful hosting plan, but it isn't. A Wordpress blog with 20 plugins can serve only 10-20 odd users in parallel which a lightweight Wordpress installation can handle up to 50 concurrent users as well. A good benchmark is to observe your analytics stats - if you see the peak usage always flattening out at a given user count then you know that it is time to move to a more powerful server.

Need for Running Custom Software

Beyond a point, it becomes impossible or prohibitively expensive to scale your site using hardware alone. At such times, changing the technology stack to be more stateless and light-weight becomes a more cost effective solution. In such cases, you often need to install more packages or move your technology implementation to a customized solution. Doing this on a shared host is very challenging as you don't have administrative access to your machine.

Security Considerations - Value of Transactions / Type of User Data Stored

Conclusion

This article is mainly for webmasters running web apps like Wordpress and Magento on shared hosting. While beginner's web hosting guides will usually suggest shared hosting to start with given its cost and complexity, shared hosting has its limitations which become more prominent as your site becomes more popular. It is usually critical to know when to move from your cost-effective shared hosting to a more powerful but expensive Virtual Private Server (VPS). There are 3 factors which influence the need to switch to VPS as below.

Number of Users / Sessions / Transactions

I wish it was as easy as giving a number of users or sessions which serve as a threshold to moving to a more powerful hosting plan, but it isn't. A Wordpress blog with 20 plugins can serve only 10-20 odd users in parallel which a lightweight Wordpress installation can handle up to 50 concurrent users as well. A good benchmark is to observe your analytics stats - if you see the peak usage always flattening out at a given user count then you know that it is time to move to a more powerful server.

Need for Running Custom Software

Beyond a point, it becomes impossible or prohibitively expensive to scale your site using hardware alone. At such times, changing the technology stack to be more stateless and light-weight becomes a more cost effective solution. In such cases, you often need to install more packages or move your technology implementation to a customized solution. Doing this on a shared host is very challenging as you don't have administrative access to your machine.

Security Considerations - Value of Transactions / Type of User Data Stored

It is well known fact that if one account on a shared hosting server is compromised, then it is far easier for a hacker to access / destroy data from other accounts on the same server. With VPS, your security is not dependent on other's foolishness and hence your data is more secure. If you have the need to store PII data or are processing a significant amount of dollars in transactions, then you need to move to a VPS host at the earliest.

Conclusion

As a webmaster, you need to be consistently aware of these factors and to what extent they apply to your website. The moment you see any of them affecting your website, you must start the migration process to a good VPS host immediately. You might want to go through the list of the best VPS providers.