We’ve all had the annoying experience of clicking on a website or opening an app only to find it’s down for maintenance or not working. In that situation, we’re either left frustrated that we couldn’t do what we needed to, or even in some cases, look for what we want elsewhere. 

That’s why downtime is such a serious business: ultimately, it can mean lost sales and spoilt customer relationships. While updates and maintenance are necessary, users want an uninterrupted service, which makes zero downtime deployment (ZDD) the ideal approach. 

ZDD allows you to make the required changes in the background without affecting the user experience. But how does it work in practice? We’re going to cover strategies, tools, and best practices that can help you achieve successful zero-downtime deployment. 

What is Zero Downtime Deployment? 

Traditional deployment methods usually require that a web application goes temporarily offline whenever any updates need to be made. This is counterproductive to overall business objectives and therefore something that senior management and business architects are keen for development teams to avoid.

A zero downtime deployment strategy makes it possible to make changes without disrupting usual service, with techniques like blue-green deployments or canary releases. We’ll go into more detail on those later, but the general idea is to introduce changes gradually, and closely monitor the progress. 

This means there is less risk of things going wrong and users get a continuous experience, which helps keep them happy and engaged. Plus, it can make the difference between a customer choosing your business or straying to a competitor.

Zero downtime deployment also improves operational efficiency, as the pressure and the risks that come with traditional deployment are minimized. No elaborate planning is needed to take the system offline and coordinate multiple teams, as automated processes and continuous integration are used for a faster development cycle and less stressful deployment. 

Key Strategies for Zero Downtime Deployment 

ZDD is not just a single technique but a combination of strategies that take different approaches to minimizing disruption to user experience (UX) during deployment. 

Blue-Green Deployments

For this method, two identical environments are maintained: the active (blue) environment and the idle (green) environment. Initially, updates are deployed to the idle environment, allowing teams to conduct thorough testing without any impact on users. 

Once everything has been verified, the traffic is switched to the green environment, and so the updated version goes live without any downtime. The main upside of this approach is that if any issues arise, it’s possible to quickly revert back to the blue environment. The downside is that blue-green deployments require double the infrastructure, which makes it an expensive choice. 

Canary Releases

In the case of a canary release, updates are rolled out to a small group of users, known as the canary group, before they are deployed to the entire user base. The team can then monitor the stability and performance of the new release under controlled conditions. Any issues that come up will only have minimal impact in the context of the wider user base. 

This is a great way to validate new features or changes without risking all users encountering potential bugs. However, it’s important to note that very careful monitoring and a quick response system are essential to tackle any issues that arise in the canary group. 

Rolling Updates

A rolling update makes incremental changes to applications across servers, one or a few at a time. Traffic is, therefore, able to continue uninterrupted through the unaffected servers. This creates a balance between canary releases and blue-green deployments, as there is an incremental update alongside targeting specific servers (as opposed to users). 

The result is a continuous deployment model that copes with live traffic effectively. Rolling updates are popular because they’re resource-efficient, as there is no need for duplicate environments. However, they do require careful management of load balancers and monitoring systems so that updated and non-updated servers can interact without causing problems. 

Feature Toggles

Feature toggles are used to deploy code changes with new features that are turned off by default. The idea is that they can then be selectively turned on for specific users or environments, giving teams control over the visibility of features without full deployment. 

It’s an approach that supports iterative testing and experimentation, meaning it aligns well with a broader UX strategy by allowing features to be tested and refined based on real user feedback. The drawback is that managing toggles can become complicated, particularly when the number of toggles increases, requiring disciplined cleanup and version control.

Technical Considerations and Challenges 

When implementing zero downtime deployment, you need to be prepared for these technical considerations and common challenges. 

Database Changes

Updating a database schema with zero downtime represents a significant challenge. There are a few strategies you could try to tackle this issue, such as: 

• Using backward-compatible changes
• Using new fields rather than altering existing ones
• Using database versioning techniques.

It may also be wise to adopt a phased approach, whereby the database is updated in stages – first to support the old and new application versions and then to refine it once the transition is complete. This keeps the application functional throughout the deployment. 

Load Balancing

When you’re managing traffic flow during updates, effective load balancing is of utmost importance. Load balancers always play an important role in distributing traffic evenly among servers, to avoid overloading and potentially ruining your website’s user experience. During ZDD, they become even more important, as they must direct traffic only to the servers working correctly.

To make sure service continuity is maintained, employ techniques like session affinity to keep users sessions on the same server, or health checks to automatically redirect traffic away from a problematic server. When properly configured, load balancers help prevent disruption and keep performance levels consistent. 

Monitoring and Rollbacks

The impact of deployment must be closely monitored to spot any issues early before they cause major problems. Real time monitoring tools should be used to flag when any errors crop up or performance degradation occurs.

A rollback plan should also be established, so that when issues arise, you can revert back to the stable version. Wherever possible, automate rollbacks to minimize reaction time: problems will then be nipped in the bud as swiftly as possible and the effect on UX will be negligible.

Tools and Testing

The effectiveness of zero downtime deployment is highly dependent on the tools and practices employed. 

Essential tools

These are three of the technologies most vital to zero downtime deployment. 

• Kubernetes: This tool manages containerized applications across multiple hosts, making it easier to handle scaling and deployment without downtime.
• Docker: Lightweight containers create consistent environments from development through to production, allowing this solution to reduce issues related to differences in configuration.
• Jenkins: A technology that automates the CI/CD pipeline, handles builds, tests, and deployments to speed up release cycles and reduce human mistakes.

Continuous Integration/Continuous Deployment (CI/CD)

Much of the deployment workflow can be automated with CI/CD pipelines. Continuously integrating new code changes and deploying them automatically means these pipelines can be rolled out quickly and with little risk of disruption. This is an approach that is considered integral to ZDD, as it keeps the user experience reliable and stable. 

Testing

Automating testing provides the chance to check updates for problems before deployment. Testing can be integrated into the CI/CD pipeline to catch any issues early on, creating a safety net that stops faulty updates from reaching users.

In the future, this is likely to be an area where we increasingly see the impact of machine learning in web development, as it optimizes and speeds up the development cycle and makes testing more efficient and accurate.

Implementation Tips and Best Practices

The best place to start to make sure zero downtime deployment runs smoothly is with gradual implementation. Begin with non-critical services first, before scaling up as the team gains experience and confidence with the process. This gives everyone the opportunity to learn and make adjustments in the early stages, so you have the best chance of success when it comes down to the big changes. 

With ZDD, it’s also important to remember that team collaboration is vital. All relevant parties, including developers and operations teams, must be aligned on the deployment strategy and should fully understand the potential effects. Tools like Ardoq can help you map dependencies and visualize the impact of deployment across the organization, all of which support better communication and collaboration.

Finally, as with any kind of deployment, risk management is essential. Although you can take every precaution to make sure everything goes well, you need a plan for dealing with potential failure that includes a solid recovery plan. Consider automated rollbacks or failover strategies to help deal with the unexpected and protect the continuity of user experience. 

Keep UX consistent with ZDD

With zero downtime deployment as an option, interrupted user experience is no longer necessary. You can update applications whilst still maintaining a continuous service. 

This keeps users happy with an uninterrupted service and stops customers from taking their business elsewhere. Zero downtime deployment really is the best solution for both web development teams and the wider business. 

Featured image by Nangialai Stoman on Unsplash