Refactoring vs rewrite – which is better for your web application?

Every growing web app eventually reaches a point when better performance and functionality must be handled. Sometimes there are bugs to fix, the app slows down, or the current technology does not allow further development at a good pace. In such cases, it is worth thinking about upgrading the code. In this article, we compare refactoring vs rewrite and advise on which method to choose depending on the specifics of the project.

Legacy Project modernisation techniques

Let us first clarify the basic terms we will be using. Since we are talking about code modernisation, we mean various techniques that aim to improve the performance and code maintainability of a web application. Perhaps it was developed several years ago and the technology is outdated, or the code is complicated. It is possible that, as the company grows, the database handles more and more queries, so the system loses performance. Sometimes bugs creep in and some functionalities stop working, or the application fails to meet business objectives.

When we take on code modernisation, we usually deal with legacy projects. In short, it is software that is critical to the business or performs multiple processes. The implementation of legacy projects is usually very complex and introducing new changes is risky. We cannot cause downtime for a business-critical application. On the other hand, changing one functionality may affect the operation of other elements. Past mistakes may also come to light during optimisation, making further work more difficult.

Upgrading the code in legacy projects requires a careful analysis of the situation. The choice of method (i.e. refactor or rewrite) depends on the current state of the web application and the effect we want to achieve. And, of course, this whole process has to be profitable from a business perspective.

What is an application refactor?

Refactor is a method of optimising existing source code by improving readability of the code. The premise of this method is, among other things, to improve the performance of an application or its functionalities without writing all the code from scratch. This avoids downtime and major changes in a short period. This action should not affect the entire system's behaviour; thus, users do not need to re-learn how to use the application. It is a good idea to map out the key areas of the software that are causing problems and successively fix them.

Refactoring a web application – advantages and disadvantages

The most important advantage of this approach is the ability to modify selected parts of the code instead of creating it from scratch. This makes it possible to increase performance and security gradually and scale the application without incurring a large cost. Refactoring is also worth utilising when you want to start using a new programming technology. In this situation, you can keep some functionalities in the old system and some in the new one. As a result, users will not experience abrupt changes in application performance.

However, there are also risks associated with this approach. If the system uses outdated technology, finding the right team to refactor the web application can be a problem. You may find that the code is written in the 'old style', which means its architecture does not take into account current standards and good programming practices. Then, you may come across bugs covered by patches. Eliminating them will certainly have consequences in other areas of the system. Such surprises can significantly increase the time spent working on a project and cause many unnecessary costs.

What is an application rewrite?

Rewrite is, in fact, the creation of a completely new web application. As a rule, this solution is used when other options have been exhausted. This process is usually more expensive (but it doesn't always have to be) and allows the system to be transferred to a completely new technology and new code standards to be developed. All functionalities are developed from existing software. However, there is no problem making modifications. Rewriting the application may be the only option when we cannot access the old code or its quality is poor.

Web application rewrite – advantages and disadvantages

A complete rewrite of a web application opens up the possibility of using newer technologies and tools to improve performance and security. This approach allows the creation of a more scalable system. Current programming standards assume optimisations that were unknown in the past. Sometimes the software is based on a technology that is no longer used or developed. In such cases, rewrites can help adapt the application to the changing technological environment. It gives greater flexibility in creating a new system, functionality, and layout.

This approach, however, also has its downsides. Firstly, a complete rewrite of the code is expensive and takes a lot of time. This is a really big investment that will not always make economic sense. Besides, a working system is usually much more complicated than it appears. Many important system functions may simply not be documented. It is, therefore, difficult to test whether the new system will behave the same way as the old one. For this reason, it sometimes appears that the new system is not at all more efficient than the previous one.

Remember that your web application is supposed to fulfil a business function, so rewriting code is not always cost-effective. However, it is intended to improve many areas simultaneously, including functionality, performance, user experience, system scalability, and ease of use for developers in the future.

Refactoring vs rewrite of the web application – which method to choose?

When comparing refactoring vs rewrite, it's crucial to consider the time and resources available. In most cases, the web application refactor should be the default option. By design, it is a shorter, easier and less expensive process. It's a good solution to correct bugs in the code and improve performance and security. Old projects are often not optimised for code hygiene, automation and testing. Therefore, unless the code has extremely poor quality and the technology is too outdated, refactoring will probably allow the application to work better.

Sometimes, when the code is too complex and the system functions are strongly dependent on each other, refactoring can have unexpected consequences. Hidden errors can cause a lot of problems and fixing everything will cause additional difficulties and costs. Therefore, in each case, the code architecture, user behaviour or opinion of app functionalities should be analysed in detail before upgrading the code.

In some cases, rewrite may be a better option. For small projects, creating a web application from scratch will not be as problematic or expensive. So, it may still be worth rewriting it, taking into account scalability and changing technologies. Large projects will be much more demanding. If the old system works but needs refreshing, a complete rewrite is unlikely to make any sense. In this case, it is worth considering incremental rewrite. In this approach, you can simultaneously maintain the old code and slowly, piece by piece, add new features. This requires two layers of code to be maintained, so you should firmly separate them.

Refactoring vs rewrite of the web application – summary

Choosing between refactoring vs rewrite is a challenging decision. On the one hand, we have a system that works; on the other, we strive to innovate and use the latest technology. However, it is worth remembering that this new technology will also be obsolete in a few years. Above all, the web application is primarily designed to meet business targets.

When implementing new software, the change should not be too abrupt. Be sure to carry out user research to find out what problems are relevant and which areas need priority improvement. Consider maintaining two versions with the ability to switch quickly between them. Testing new functionalities on a small group of users may also be a good solution. Each change should be documented to keep project transparency and to be able to make decisions on code upgrades more easily in the future. We hope that our comparison of refactoring vs rewrite will allow you to choose the right method. If you would like to find out more information, feel free to contact us.