A code review is a structured examination of source code by at least one other person in the team. For clients, code review is not an end in itself, but a way to make software easier to understand, maintain and extend.
Good code quality affects how much effort is needed for bug fixes, changes and later development stages. That is exactly why the topic is not only technical, but also relevant to business decisions.
A code review does not replace business acceptance checks or tests, but complements them at a different point in the project; the article on business acceptance checks and tests shows how tests fit into the picture.
This article explains, without any programming code, how a code review works, what you as a client can look out for, and when the effort is particularly worthwhile.
Why code review matters for clients
Source code is the human-readable foundation of a piece of software from which the application is created. This matters for clients because it is at this level that it becomes clear how well a solution can later be maintained, extended and understood.
The topic becomes commercially relevant wherever software is not created just once, but used over a longer period. If the code is unclear, inconsistent or unnecessarily complex, later changes often become slower and more error-prone. This affects not only individual functions, but also adaptations to new processes, additional interfaces and the further development of existing applications.
Maintainability is therefore a business factor. A project does not usually end after go-live: business requirements change, processes are adjusted and systems need to be connected. Cleanly structured code can usually be adapted more easily in these situations than one-off solutions that have grown over time.
A code review helps to make risks visible earlier, before they spread across several modules or interfaces. For non-technical readers, this can also be put like this: it is about avoiding future friction that starts small today.
This also fits with the term technical debt. This means shortcuts in development that may save time at first, but cause additional effort later.
Another important point is this: code quality does not concern individual developers alone, but the long-term usability of the entire solution. If several people can understand the code, the project depends less on the knowledge of individuals. That improves cover, collaboration and the basis for future development. If you would like to get an idea of the scope of your project, ballmüller solutions' services, the cost calculator for a rough price range, the project check based on your documents, contact for a no-obligation initial meeting and insights into reference projects can help.
What is checked in a code review
A code review should not be a matter of personal taste. It is not about whether someone personally prefers a certain style of writing, but whether a change has been implemented in a way that is understandable, consistent and robust according to clear criteria.
A key point is clarity. Others in the team should be able to see what a section does, why it is structured that way and what business intention lies behind it. If a change only makes sense with the additional knowledge of one individual, that creates unnecessary dependency later on.
Consistency is just as important. Similar tasks should be solved using similar patterns within an application. That makes maintenance easier, because new changes are easier to place in context and the software does not end up consisting of many isolated solutions that are hard to compare.
The review also looks at how prone the code is to errors. This includes, for example, edge cases, incomplete checks or assumptions that do not always hold true in day-to-day use. These are exactly the kinds of issues that often become visible when a second person looks at the change with a bit of distance.
Another review aspect is interfaces. Interfaces are defined connections between systems or modules through which data is exchanged. Clarity and robustness are especially important here, because changes in these areas often affect several parties or connected systems.
Changes close to the database are also examined carefully in a review. Databases store an application's structured information permanently. That is why traceability and a clean structure matter here, so that later reporting, extensions and adjustments are not made unnecessarily difficult.
In short, a code review does not only look at whether something works, but also at whether the implementation is sustainable for ongoing operation and further development.
How a code review works in a project
In practice, code reviews work best when they are built firmly into the development process rather than carried out only occasionally as a special task. That creates a recurring, traceable step within delivery.
Typically, a code review follows several clear steps:
- A developer submits a completed change for review. What matters is that the change makes sense as a whole and serves a clear business or technical purpose.
- Small units are an advantage here. Manageable changes are easier to follow and assess properly than very large packages in which many topics are mixed together.
- A second person reviews the change against agreed criteria. For example, they look at clarity, consistency, possible risks and unnecessary complexity, and comment on parts that seem unclear or problematic.
In many projects, this happens via a pull request. This means a bundled submission of a change for joint review within the team.
After that, it is not simply a case of ticking off comments. Questions and feedback are discussed so that a shared understanding can emerge. This matters because a code review should not only find faults, but also strengthen the team's shared way of working.
The change is then revised and briefly checked again. This step may be repeated until the implementation can be incorporated into the shared codebase.
Only after that, depending on the project, do further quality assurance measures follow. These may include automated tests, meaning software checks that run automatically, business checks by the responsible stakeholders, and deployment of the change to the next environment or to go-live.
For clients, the key point above all is this: a code review is not an isolated extra, but part of a structured path towards software that is understandable and maintainable.
When the effort is particularly worthwhile
The value of code review increases wherever decisions in the code have long-term effects. This applies above all to projects in which a solution is not only introduced, but must also be adapted over time, expanded and understood by several parties.
It is particularly relevant in cases such as these:
- when existing software is being replaced and business rules need to be rebuilt in a new and clean way
- when established applications are being extended without further reinforcing unclear structures
- when several teams, business units or external parties need to work together in a coordinated way
- when interfaces, data structures or core processes are affected, where later changes often have knock-on effects
Examples from practice also show why this step is worthwhile: for a web platform for managing a sewer network, for a CRM system or for an extension with an external connection. In these kinds of constellations, what matters is that changes do not only work, but also remain understandable for later work steps.
AI functions also deserve particular attention, for example for searching company knowledge, assistants or document extraction. Here in particular, it makes sense for the implementation to remain understandable within the team and for assumptions not to sit only with individual people.
Code review is therefore especially useful wherever software is meant to last beyond its initial functional scope.
Questions clients often ask about code review
Do I still need a code review if the software is already being tested?
Yes, in many cases you do. Tests and code review examine different things. Tests mainly show whether a function delivers the expected result under certain conditions. A code review also looks at whether the implementation is understandable, consistent and suitable for later changes. That makes issues visible which often do not show up in a test, such as unnecessary complexity, assumptions that are hard to follow or risky effects on neighbouring areas.
Does a code review slow the project down, or save effort later?
In the short term, a review is an additional step in the process. So at first it does take time and coordination. In many projects, however, that effort can help later because problems are spotted earlier and changes remain easier to follow. Whether the step is worthwhile depends above all on how long the software is meant to be used, extended or connected to other systems. The more important maintenance and further development are, the more likely good review practice is to make commercial sense.
How can I tell as a client whether code reviews are being carried out seriously in the project?
Not from individual technical terms, but from the way the work is done. Useful signs include, for example:
- Code review is planned as a fixed step in the development process.
- There are clear criteria rather than just individual opinions.
- Questions and feedback lead to agreed adjustments.
- Changes are reviewed in manageable units.
- Quality assurance is explained as the interaction of review, tests and business checks.
If a service provider can describe the process clearly, that is usually more meaningful for clients than technical jargon.
Is code review only useful for large projects, or also for smaller enhancements?
Not only for large projects. Smaller enhancements can also affect existing processes, interfaces or data structures. That is exactly when a second review is helpful, because small changes in established applications can often have bigger consequences than first appear. The scope of the review can be matched to the project.
Can a code review also help with existing applications that are to be extended or replaced?
Yes. In existing applications, a review helps to assess current structures more clearly and make risks more visible before a change is made. This is particularly useful when an application has grown over a long period or knowledge sits heavily with individual people. It also helps during replacement work, so that unclear points and problematic patterns are not simply carried over into the new solution.
Considering code quality early on
Code review is a practical way to keep software understandable, maintainable and easier to extend. For clients, that does not mean having to assess every technical detail. More important is understanding that code quality has a direct impact on later changes, handovers and collaboration in the project.
Anyone planning, replacing or extending software should therefore raise this point early.
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