What is Site Reliability Engineering?

An Introduction to SRE

SRE or site reliability engineering has become increasingly essential as businesses confront an ever-growing IT infrastructure that manages cloud-native services. One of the reasons is that the way software development and deployment teams operate has altered considerably.

DevOps principles, which include continuous integration and deployment, have fueled the adoption of DevOps concepts and a transition from departmental silos to a new engineering culture in an ever-changing world. This way of thinking endorses and lives the “you build it, you run it” mentality.

Site reliability engineers are hired by businesses to keep their new IT architecture stable and enhance their competitive advantage. SREs use a variety of engineering principles to assist product engineering teams in optimizing their processes. The team’s fundamental objective is to develop highly dependable software systems by analyzing the current infrastructure and finding methods to improve it with software solutions.

In this post, you’ll discover more about the function and advantages of site reliability engineering, the fundamental principles utilized in SRE, as well as the distinction between a site reliability engineer and a platform engineer.

What is Site Reliability Engineering?

Site reliability engineering, also known as SRE, is a software engineering method that aids in the management of large systems via code. It’s the job of a site reliability engineer to develop a stable infrastructure and efficient engineering processes by following SRE standards. This also includes the use of monitoring and improvement tools as well as metrics.

Even though SRE appears to be a relatively new position in the world of cloud-native application engineering and management, it has been around even longer than DevOps – the phenomenon that successfully connected software development and IT operations.

In fact, it was Google that entrusted its software engineers to make large-scale sites more dependable, efficient, and scalable through the use of automated solutions. The procedures that Google’s engineers began experimenting with in 2003 are now part of the full-fledged IT domain.

Site reliability engineering, in a sense, takes on the responsibilities that operations teams previously performed. However, operational difficulties are addressed with an engineering approach rather than a manual one.

With the use of sophisticated software and Site/Environment Management tools, SREs may establish a link between development and operations to create an IT infrastructure that is dependable and allows for easy deployment of new services and features.

Site reliability engineers are especially important when a firm switches from a traditional IT approach to a cloud-native one. Next, discover more about the responsibilities of a site reliability engineer and what sort of talents are required in this line of work.

What does a Site Reliability Engineer (SRE) do?

A site reliability engineer is someone who has a background in software creation as well as significant operations and business intelligence expertise. All are required to deal with technical issues using code. While DevOps focuses on automating IT operations, SRE teams focus more on planning and design.

They track operations in production, and ideally in non-production (shifting SRE Left), and study their performance to find areas for improvement. Their comments also assist them in predicting the cost of outages and preparing for contingencies.

SRE Engineers will divide their time between operations and the development of systems and software. On-call duties include updating run sheets, tools, and documentation to ensure that engineering teams are ready for the next emergency. They generally conduct deep post-incident interviews to figure out what’s working and what isn’t after an incident occurs.

This is how they acquire important “tribal wisdom.” Because they engage in software development, support, and IT development, this information is no longer compartmentalized and can be put to use to build more reliable systems.

A site reliability engineer’s work is also spent developing and enabling services that improve operations for IT and support personnel. This might imply creating a new tool to repair the flaws in current software delivery or incident management.

And last but not least, SREs are in charge of determining whether new features can be added and when, utilizing the aid of service-level agreements (SLAs), service-level indicators (SLIs), and service-level objectives (SLOs).

Learn more about SRE key performance indicators SLA, SLI, and SLO in the following section, as well as how they are used in site reliability engineering.

The difference between SLOs, SLIs, and SLAs

Site reliability engineers employ three metrics to monitor and improve the performance of IT systems: They write service-level agreements (SLAs), service-level indicators (SLIs), and service-level objectives (SLOs). These related service level measurements not only assist firms in building a more dependable system but also increase consumer confidence.

Let us define each of these key SRE metrics in more detail.

SLI Metric

SLI stands for the service-level indicator. An SLI measures the qualities of service, to provide input for a service provider’s objective.

  • Referencing the SRE Handbook, Google defines it as “a carefully defined quantitative measure of some aspect of the level of service that is provided.”

The analysis of behavioral data is a critical part of any successful customer experience optimization program. Four golden signals are the most frequent SLIs: latency, traffic, error rate, and saturation.

When SRE teams build SLIs to assess a service, they usually use two stages.

  1. They determine the SLIs that will directly impact the customers.
  2. They determine which SLIs influence the availability or latency or performance of the service.

SRE SLI Formula

The formula used to calculate ones SLIs is:

  • SLI = (Good Events * 100) / Valid Events

Note: An SLI value of 100 is optimal, whereas a drop to 0 means that a system is broken.

It’s critical to build SLIs that are appropriate for the user’s experience. This implies that a single SLI is not capable of capturing the whole customer experience as a typical user may be concerned with more than one thing while using the service. Simultaneously, creating SLIs for every imaginable statistic is not desirable since you would lose focus on what matters most.

Site reliability engineers generally focus on the most pressing problems as users go through a system. Once the SLIs have been established, an SRE connects them to SLOs, which are important threshold values defining the availability and quality of service.

SLO Metric

The SLO or service level objective is used to assess the quality of a service’s reliability or performance criteria.

  • Referencing the SRE Handbook, Google says that they “specify a target level for the reliability of your service” and “because SLOs are key to making data-driven decisions about reliability, they’re at the core of SRE practices.”

Unlike SLIs which are product-centric, SLOs are customer-centric.

Their relationship can be defined as follows:

  • SLO (Lower bound) <= SLI <= SLO (Upper bound SLO)

However, establishing appropriate SLOs is a difficult process. Targets should generally be established based on historical system performance rather than current conditions. And targets should be realistic, as opposed to too ambitious.

Tip! Absolute values are not required. It is often better to identify a “realistic” range based on historical data.

SLOs should be viewed as a unifying mechanism that fosters a cohesive language and shared objectives across various departments. And you’re considerably more likely to succeed if all key stakeholders are on board.

However, many firms are preoccupied with product innovation and fail to recognize the link between business success and dependability. Siloed data and the mistaken belief that once standards have been established, they don’t need to be re-examined or adjusted are two frequent stumbling blocks.

SLA Metric

A service-level agreement, or SLLA, is a contract that specifies the level of service provided by a platform. Similar to SLOs, service levels are a client-focused measure.

  • Referencing the SRE Handbook, Google says, an SLA is defined as “an explicit or implicit contract with your users that includes consequences of meeting (or missing) the SLOs they contain.”

An SLA is triggered as soon as an SLO is “breached”. In most cases, you should anticipate fines and financial repercussions if you do not fulfill the requirements of the SLA. If your firm breaches a term established in the SLA, it generally has to repay its clients.

Service-level agreements (SLA) provide transparency and trust between the company and its consumers. They’re similar to SLOs, but instead of being used by a business, they apply to external rather than internal activities. SLAs are less conservative than SLOs, implying that the value of reliability is always somewhat lower than the historical average of an availability SLO. This can be seen as a safety precaution if the average is set too high because there were just a few incidents in the past.

In Conclusion

Site reliability engineering is a critical process for ensuring that websites and online services are available and functioning properly. By establishing key metrics and thresholds, SREs can prevent outages and disruptions in service. SLAs, SLOs, and SLIs are three important tools that SREs use to measure and manage system performance. To be successful, SREs must have a deep understanding of these metrics and how they relate to one another.


The Top Deployment Strategies Explained

As a DevOps engineer, you need to be familiar with various software deployment strategies and know when to use which one. In this article, we’ll look at what software deployment strategies are available, how they work, and the typical strengths & weaknesses of each.

In software development, a deployment strategy is a set of instructions that dictate how our software code or applications should be transferred from one environment to another during the software development life cycle.

What is a Release

The process of “shipping” new features or bug fixes, usually more than one, to users is known as a software release. A software release can be a patched version, a major new version, or a hotfix for an issue found in a previous version. Software releases go through several development stages before they are ready to be made available to users (in what is called production).

A typical software development life cycle includes the following stages:

  • Development
  • System, Integration, and User Acceptance Testing
  • Staging
  • Production

Your deployment process, or deployment plan, defines the rules and steps of how software code should be moved (or deployed) from one stage to the next. It is important to have a well-defined deployment strategy because it will help ensure that code changes do not break the software in production and that users always have access to the latest version of the software.

To complete this important job, the DevOps team incorporates deployment procedures into their day-to-day operations. Various approaches have been developed throughout time to help software companies with application deployments.

What Is a Deployment Strategy?

A deployment strategy is a technique used by DevOps teams to launch a new version of their software. These strategies cover how traffic is transitioned from the old version to the new version and can influence downtime and operational cost. Depending on the company’s specialty, the right deployment strategy can make all the difference.

Various Types of Deployment Strategies

There are several types of deployment strategies, each with its advantages and disadvantages. The right strategy for your company will depend on your needs and goals.

1. Blue/Green Deployment

This type of deployment process involves maintaining two identical production environments—one is the “live” environment that serves customers, while the other is the “staging” environment. When it’s time to release a new version of the software, the staging environment is switched to live, and vice versa.


  • This strategy minimizes downtime because there is always a production environment available.


  • However, it can be costly to maintain two identical production environments.

2. Canary Release

In this strategy, the new version of the software is first released to a small subset of users. If there are no major issues, the new version is then gradually rolled out to a larger subset of users until it is finally made available to the entire user base.

For example, the older version may retain 90% of all traffic for the software at a certain point in time during the deployment process, while the newer version hosts 10% of all traffic. This method helps DevOps engineers to test the new version’s stability. It utilizes real traffic from a fraction of end-users at different phases throughout production.


  • Better performance monitoring is possible with Canary deployment. It also aids in the quicker and more successful rollback of software if a new version fails.


  • However, it does require more effort and typically, a long deployment cycle.

3. A/B Testing

May, also be called Incremental Rollout

In the A/B testing deployment process, developers deploy the new version alongside the older version. This type of testing is used to compare two versions of a software feature to see which performs better. Version A is the control and is made available to the entire user base, while version B is the test and is only made available to a subset of users.

A/B testing has several deployment process benefits:

  • It allows software developers to compare two versions of a software feature to see which performs better.
  • It is easier and less risky to test a new version of the software on a small subset of users before rolling it out to the entire user base.
  • Developers can easily accept/reject either version.


  • Increased user/customer coordination.

4. Feature Toggles (Feature Flags)

Feature flags are a type of deployment strategy that allows developers to turn on or off certain features of the software for different users. This allows developers to test new features without making them available to the entire user base. Feature flags can be used in conjunction with other deployment strategies, such as A/B testing, to help developers test new features before

5. Recreate Deployment

In this deployment approach, the development team completely shuts down the old software, then deploys and reboots the new version. This method causes a system outage between shutting down the old program and booting up the new one.


  • It is less expensive and is primarily utilized when the software company wishes to rewrite the application from the ground up. There’s no need for a load balancer since there are no changes in traffic flow in the live production environment.


  • This method has a significant impact on end-users since it is unavailable/suspended. Users must wait until the software is reactivated before using it. As a result, few developers employ this technique unless they have no other option.

6. Trunk-Based Deployment

In this strategy, all code changes are first merged into a main trunk or branch. Developers then create a new branch for each new feature. Once the feature is complete, it is merged back into the main trunk. This strategy eliminates the need for long-running feature branches and makes it easier to deploy new changes.

Note: This is more a pre-deployment method of Software Version Control.

7. Ramped Deployment

The ramped deployment method moves from one version to the next in a gradual process. Unlike canary deployment, which replaces instances of the old application version with those from the new application version one at a time, the ramped deployment approach makes its change by replacing instances of the old application version with new applications. The rolling upgrade deployment strategy is another name for this method.

The second method, as the name implies, is to delete the old version from production. When all of its instances are deleted, the older edition is manually shut down. The new edition then controls all production traffic.


  • No need to take the entire application offline for an upgrade.
  • The process is gradual, so it’s less risky.


  • Takes longer to complete than other methods.
  • Requires more instances to be available during the process.
  • Rollback is more complicated & long.

8. Rolling deployment

For those using containers.

Rolling deployment is a gradual process of replacing pods running the old version of the application with the new version, one by one, without downtime to the cluster. It is less risky and takes longer to complete than other types of deployment, but it doesn’t require taking the entire application offline.


  • Lower Risk
  • High Availability


  • Only really applicable for container-based architectures.

9. Shadow Deployment

Developers deploy the new version alongside the existing one in this deployment method. Users, on the other hand, won’t be able to access it right away. The newest version hides in the shadows, just as its name implies. Developers send a fork or copy of the previous version’s requests to the shadow version so they can examine how the new variant will work and if it can process the same amount of requests.

When the shadow version can handle the same load as the original, the traffic is finally routed to the new version, and it becomes live. The cutover from the original to the new version happens without any significant downtime since there’s no need to take down or restart either version.


  • valuable feedback can be gathered about how the new version will work in production
  • there’s no need to take down or restart either version during the cutover process


  • more complicated to set up and maintain than other deployment strategies
  • if not done correctly, it can cause issues with the live version

When to use:

  • when you want to gather feedback about how the new version will work in production
  • when you want to avoid any significant downtime during the cutover process

Deploy Better with a Software Deployment Tool

Managing your deployments without tools can be fraught with danger.

As seen above, the different deployment processes can be quite fragile/awkward, and if done incorrectly could lead to production issues, outages, and the need to roll back.

Using tools to control your “implementation day events” can uplift visibility, improve collaboration, support rehearsal, standardize your operations and also streamline the tasks*.

*Tasks that may be manual or preferably automated.

Fortunately, there are various Release Management tools that can help your organization with the various aspects of Environments, Release Management & Application Deployment.

The best software deployment tools included features like:

  • Release Management Governance for Scale Delivery*

*for managing the End to End Release / Release Train.

  • Implementation Plans (for Deployment Planning)
  • Operational Runsheets / Standardized Operating Procedures
  • DevOps Automation e.g. Software Deployments
  • Orchestrations / Integration with other tools*

*deployment tools, ticketing tools, CI/CD i.e. continuous integration, and continuous delivery tools

  • Deployment Version Tracking

*tracking code deployments across Environment Instances, Components & Microservices.

  • Environment Drift Reports

*supporting holistic, cross-environment, version control


You may use any of these methods to upgrade your applications. Each of these approaches has advantages and disadvantages, and each is appropriate in certain circumstances. The only question now is which one makes the most sense for your DevOps team to utilize.

Consider the demands of your team, project, and company as well as corporate objectives. Also, keep track of how much downtime your business can tolerate and any other cost limitations.

Make your go-live events into non-events!

Uplift your Implementation Planning, and Deployment Management capability today. Find the best software deployment tool (or tools) to help with your automatic deployments.

Author: Mark Dwight James

This post was written by Mark Dwight James. Mark is a Data Scientist specializing in Software Engineering. His passions are sharing ideas around software development and how companies can value stream through data best practices.

Test Environment Management 101

Test Environments Management 101

Test Environment Management 101

Test environments are critical in the software development and software testing process as they allow for quality assurance testing to take place in a controlled setting. Test environments can take many forms, from simulating customer data on a test server to running performance tests on a staging environment. The key is to ensure that your test environment accurately reflects your production environment as closely as possible.

There are many ways to run tests, and most involve testing environments. This post explores test environments from the ground up. Not only will you learn what a test environment is, but who is responsible and what practices are needed.

This post will explore test environments in-depth, discussing everything from what they are to how to set them up and manage them effectively.

What is a Test Environment?

A test environment is any space in which software undergoes a series of experimental uses. In other words, it’s a place where software testing will you test your code to make sure it works as you intended.

A Test Environment is a type of IT environment that is used for the sole purpose of testing. This could include anything from functional testing to load testing and performance testing.

The main purpose of having a Test Environment is to create an isolated environment, including Test Data, in which development and tests can be carried out without affecting the live production environment.

Test environments are typically made of one or more of your applications, or systems. This includes the physical or virtual hardware, whether on-premise or in the cloud, and the operating system on which such versions of the application software will reside for the duration of prescribed test executions.

Let’s take a look at a few test environment types and gain a deeper understanding of them.

Types of environments

There are typically seven types of environments along any software’s development lifecycle:

  • Development
  • System Testing
  • Integration Testing
  • User Acceptance Testing
  • Performance Testing
  • Staging
  • Production

Each environment has a different purpose, and as such, each one runs the application in a slightly different way.

What is a “Development” Environment?

The development environment, on the far left of the lifecycle, is where the main (latest) branch of a software application is located. This is where developers spend time writing code to create a minimum viable product (MVP) from an initial concept. These environments may be shared within the team, or deployed on people on development instances, say inside a VM or Container on their laptop.

The development environment plays a crucial role in the software development process as it is here that new features or updates are first worked on. Note: It is not unusual to have these testing environments installed on one’s laptop.

What is a “System” Test Environment?

Supporting System or Component Testing, a system test environment is a non-production environment, or test bed, that is used to test the specific, standalone, functionality of a system before it is deployed to later test phases. This type of environment is typically configured to resemble the production environment as closely as possible, however, it will probably use stubs (mocks or virtual services) to mimic the behavior of up or downstream systems.

What is a “System Integration” Test Environment

The objective of System Integration Testing (SIT) is to ensure that all software applications and microservices work together as intended and that data integrity is preserved between them.

System Integration Test Environments are used to test the end-to-end integration, with a specific focus on the connection, or interface, points, and the movement of data between the systems. As such System Integration (SIT) testing environments are a combination of several systems that mimic how production systems collaborate.

What is a “UAT” Test Environment?

User Acceptance Testing (UAT) is a type of testing that is used to determine whether a software application meets the needs of the end-user. This type of testing is usually carried out by the end-user, or someone who represents the end-user, such as a business analyst.

UAT testing environments are an end-to-end representation of your Production Environment. It would normally contain one system instance for each production instance. For example, you would have a CRM UAT to represent CRM Production.

What is a “Performance Testing” Environment?

A performance testing environment is a non-production environment that is used to conduct performance tests, that is test the performance of software, typically under load. Performance tests are important to ensure that the software will be able to handle the expected number of users or transactions when it goes live.

Several different factors need to be considered when setting up a performance testing environment or test bed, including hardware requirements, software configurations, and network settings. It is important to have a clear understanding of what needs to be tested and how the results will be used before starting to create the performance testing environment.

What is a “Staging” Environment?

Following on from standard Test Environments, we have the Staging environments. A staging environment is meant to simulate production as much as possible, as such Staging Environments are usually well controlled, near-production level in size and layout complexity.

Simply put, this final non-production environment is used to provide further confidence in the software before it reaches the end destination of production. Note: A Staging Environment may also be used for supporting endeavors like Production Support.

What is a “Production” Environment?

Production Environments is the final stop for any software application. It is here that the application will be used by actual end-users or customers and here we find the production data. Given that it is supporting end users it is common to have the highest spec infrastructure deployed here, that is the highest performing resources like CPU, Memory, and Disk.

In addition, and due to the need for availability, it is common to have important systems configured in highly available and load-balanced layouts. And in conjunction, it is important to have well-defined processes and procedures in place for managing and maintaining them. These processes should cover everything from provisioning, and rollback through to incident management.

It is also important to have monitoring in place so that any issues can be identified and rectified as quickly as possible. This monitored data can also be used to help improve the application over time.

With the above in mind, who sets up these environments & how? Ultimately the Non-Production / Test Environments are managed by a Test Environment Manager.

What is a Test Environment Manager?

Test Environment Manager is a job title that refers to the person responsible for managing and maintaining Test Environments. The TEM is responsible for ensuring that the Test Environments are properly configured, maintained, and meet the needs of the IT project.

The Test Environment Manager is responsible for the day-to-day management of Test Environments, like Deployments, Incidents & Change, and may also be responsible for managing other aspects of the testing process, such as tooling and test data.

The TEM role is often filled by a technical individual, perhaps originally a system or technical test engineer, with a good understanding of the development & test life cycle.

Note: In a large organization there may be many Test Environment Managers, either dedicated to a single Testing Environment, System, and/or a Business Division.

What is Test Environment Management (TEM)?

Definition: IT & Test Environment Management is the act of understanding your cross-life-cycle IT environments and establishing proactive controls to ensure they are effectively used, shared, rapidly serviced and provisioned, and/or deleted promptly.  

The key activities to consider when managing test environments are:

  • Know what your IT and Test Environments look like through Environment Modelling.
  • Capture Demand across Projects and Dev & Test Teams and avoid testing environment resource contention via Test Environment Bookings.
  • Support Change & Incident through IT Service Management (ITSM) requests/support ticketing.
  • Proactively Manage Testing Environment Events through collaboration with Calendars & Runbooks (Standard Operating Procedures).
  • Streamlining your IT Operations, and software development lifecycle, through investment in application, data & infrastructure automation. For example consider: Provisioning, Rollback, Decommissioning, and Shake Down scripts.
  • Deliver Insights on Structure, Usage, Availability, and Operational Capability. Ideally real-time through an enterprise-level Test Environment Management tool.
  • And finally, Improving continuously through Environment Housekeeping and Optimization.

What Test Environment Management Tools are available?

Want to mature your Test Emvironment Management? Test environment management tools help to support the creation and maintenance of effective test environments by providing a way to manage different aspects of the test environment. Test environment management tools can range from reservation and scheduling to infrastructure configuration and deployment. Using these tools, organizations can improve the efficiency and quality of their testing process, as well as reduce the associated costs.

There are a variety of TEM tools available, each with its strengths and weaknesses. To choose the right tool for your organization, it is important to first understand your specific needs and requirements. Once you have a clear understanding of your needs, you can then evaluate the different options and select the tool that best meets your needs.

Some of the most popular test environment management tools include:

Each tool has its unique features and pricing structure, so it is important to compare and contrast the different options before making a decision.

To Conclude

Test environment management is a critical part of the software development and testing process, and the right test environments and TEM people can make a big difference in the quality and efficiency of your IT delivery process. In addition, adopting the correct Test Environment Management Tool will help your software teams produce and maintain high-quality test environments, accelerate TEM operations and implement important Test Environment Management best practices.