Software Engineers vs Site Reliability Engineering Explained

Myra Nizami

We discuss what software engineers and site reliability engineering are and explain their differences and their importance in the software development process.

What is Software Engineering vs. Site Reliability Engineering?

Software engineers design, develop and maintain computer software. Software Reliability Engineering (SRE) is a methodology that applies software engineering principles to operating challenges.  

To better understand the differences between the two, let’s look at each one on its own. 

What do software engineers do?

Software engineering applies engineering principles in programming code to create, develop, and maintain software solutions. That entails using the right programming language, platforms, and architectures to create solutions, which varies based on what’s being created. 

Software engineers are responsible for maintenance too, which means they test and improve software that other engineers make. Typical days for software engineers might include a mixture of designing their own systems, testing new programs, writing code, resolving incidents caused by errors in code, or improving the software for speed and other metrics. 

It depends on the team and skill sets, but that is the primary role software engineers play. In addition, software engineers are known for their analytical skills and problem-solving, which are vital qualities to succeed in the role. Software engineers need to have a strong command over programming languages and operating systems while keeping business goals in mind. They also have an understanding of how to bring software solutions to life based on client needs and create a high-quality product free of errors and bugs for the end-user.

What is the responsibility of site reliability engineering?

Now let’s look at site reliability engineering in more detail. So often, the initialism SRE gets confused with “software reliability engineering.” To an extent, it’s true since there is an element of testing. But SRE refers specifically to site reliability engineering,” which has a different meaning. 

Reliability engineering is a subpart of systems engineering and focuses solely on reliability. The primary role of SRE teams is to ensure that the system functions without failure. To judge the health of the system, the SRE teams will also look at a system's availability, testability, and maintainability. 

That means looking at whether the system functions as a whole and how it functions at a specified moment. Testing and maintenance become a part of that, but again, that would only focus solely on ensuring that the system functions as it should for customers.

Another way of judging software stability is assessing the number of good sessions. When users are able to complete all the functions they expect of your service without experiencing failures or unaccepted slowness, you can count that as a good session. Judging the rate of good user experiences can be used to build service level indicators (SLIs) and service level objectives (SLOs). This allows you to understand reliability from the perspective of your users. .

Like software engineers, SREs do need to have a strong command over the relevant programming languages and operating systems. Networking and cloud systems may be a part of that. SRE also comes with its own set of specific tools, so there needs to be a focus on that as well. Automation plays a significant role, especially when there are recurring issues – that’s when it’s time to automate the solution. It reduces workload and quickly addresses the issue at hand, balancing out the operational side.


How is software engineering different from site reliability engineering?

The key difference between software engineering and site reliability engineering lies in the kind of work being done and the role responsibilities. Software engineers are designing and building applications and services and testing how it works as a whole. Site reliability engineering focuses on improving those services and the systems that support them under the lens of reliability. 

Their focus isn’t necessarily on all aspects of the testing, but rather are looking to evaluate the chance of the solution failing and how that would affect both customers and the business. Therefore, SRE teams must ensure that software quality is always a priority and look at it from a customer-centric perspective. 

The idea of “software reliability engineering” is actually related to “software stability” or “application stability engineering.” Products like Sentry, Bugsnag, and Crashlytics (for mobile) that measure successful sessions over total sessions focus on the stability of the code itself. The focus is on actual application software instead of the customer experience of using the service. 

While both software engineering and site reliability engineering require coding knowledge, their use differs. Software engineering uses the programming language to build the solution itself, while SRE teams use programming to ensure the reliability of the software by focusing on building automation and working towards standardization.

Where does DevOps come in?

DevOps plays a significant role for both software engineers and SRE teams. For software engineers, DevOps is a way of ensuring the code they write is able to be maintained effectively by the operations teams. DevOps brings together development and operations teams, using tools like automation to improve and build upon code that software engineers are writing. While coding plays a role in DevOps, but about infrastructure management as well.

SRE teams bring that operational element into a more concrete fashion to ensure DevOps implementation. As part of their role, SRE teams will establish an error budget of how much a system can fail; this normalizes failures and gives developers room to innovate and try, even if it doesn’t quite work. As long as the errors don’t exceed the error budget, they can be confident that customers won’t be upset. After failures occur, SRE teams will use tools such as blameless retrospectives to drive systemic changes that prevent it from happening again. Teams create a culture focused on improving, innovating, and learning. 

How Blameless can help

Using the right tools for both software engineers and SRE teams is essential. Incident management is an inevitable issue that both teams will face, but how the issue is resolved matters. With Blameless, incident management becomes standardized, including automated runbooks and retrospectives using real-time incident data, enabling each incident to become learning for SRE and the engineering teams. To learn more about how Blameless helps streamline incident management and accelerate development velocity, request a free demo today