As an app testing expert with over 10 years of experience across 3500+ real devices, I often get asked – what exactly is the difference between continuous delivery versus continuous deployment? While they sound similar and have related goals, there are some fundamental distinctions between the two practices.
In this comprehensive guide, we’ll examine the core differences, benefits of each approach, when to use which methodology, and best practices for implementation. Whether you’re just getting started with continuous practices or looking to choose between delivery and deployment, this guide has you covered!
What Are Continuous Delivery and Deployment?
First, let’s clearly define these terms:
Continuous Delivery is a software engineering practice where application changes are automatically built, tested, and prepared for release to production. Teams can deploy changes frequently and reliably by relying on automated pipelines and rigorous testing. The key aspect is there is still manual intervention required before changes reach users – human approval is needed to release.
Continuous Deployment goes one step further – validated application changes from the pipeline are automatically released to customers without any manual approval. There is an automated trigger to push all changes that pass tests straight to users. Human intervention is completely removed from the release process.
So in summary, the core difference lies in the level of manual control versus automation. Continuous delivery allows for manual release approval, while continuous deployment relies entirely on automated pipeline triggers for production deployment. But their overarching goals remain similar – to accelerate and improve the software delivery process.
Understanding Continuous Practices
Before diving deeper, it’s useful to understand where continuous delivery and deployment fit in the broader software development landscape.
These methodologies emerged from agile and DevOps movements in the 2000s. As teams adopted agile practices, they needed ways to release software faster without compromising stability. And as DevOps gained traction, teams focused on improving collaboration and automation across build, test, and release stages.
Continuous integration (CI) became critical for frequent code integration. Automated testing helped verify changes at each stage. Teams also started treating infrastructure as code and implementing process metrics.
These capabilities culminated in continuous delivery and deployment practices that boosted release velocity. Though the ideas took root earlier, commercial tools and cloud infrastructure have made both delivery and deployment far more achievable for modern teams.
Continuous Delivery in Depth
Now that we’ve seen the background, what exactly does continuous delivery entail behind the scenes?
Continuous delivery focuses on automating and standardizing the build, test, and release process via pipelines. This means developers can sustainably release incremental app changes frequently and reliably. Some key principles include:
- Automated building – Code changes trigger pipeline jobs to compile code and assemble release artifacts
- Automated testing – Comprehensive test suites verify business logic, UX, security, etc.
- Deployment pipelines – Changes flow through dev, test, staging, and prod environments before release
- Infrastructure automation – Environments use infrastructure-as-code for consistency
- Monitoring – Production apps are closely monitored for operational issues
- Fast feedback – Telemetry data fuels rapid iterations and improvements
According to the State of DevOps Report 2022, around 69% of high performing teams leverage continuous delivery compared to just 31% of low performers. Atlassian also found delivery can reduce deployment pain by 84% and time-to-market by 50-75% based on client data.
So in summary, continuous delivery introduces a reliable, low-risk release process and gives teams extensive control over the timing of customer deployments.
Continuous Deployment Demystified
Continuous deployment takes automation to the next level. Let’s unpack how it works:
Continuous deployment means teams can sustainably release app changes to users automatically whenever code meets predefined requirements. It builds on continuous delivery principles but relies on an automated go/no-go decision for deployment instead of manual approval.
This means developers merge code frequently that kicks off a familiar automated pipeline. But once changes flow through the pipeline and pass all test gates, they are directly and instantly released to customers without any human intervention. There is no button to push or formal approval needed.
DORA research shows elite performers deploy 200x more frequently than low performers, with lead times under an hour. Continuous deployment plays a major role in achieving these metrics.
Overall benefits include lightning fast user feedback, greater agility responding to market dynamics, and less opportunity for human errors during releases. However, it requires extreme rigor around test automation and operational practices to sustain this velocity and risk appetite.
Key Differences at a Glance
Now that we’ve defined the core practices, let‘s analyze some key differences:
| Continuous Delivery | Continuous Deployment |
| Allows for manual approval or triggers to deploy changes to users | Uses fully automated triggers to deploy changes once pipeline tests pass |
| Provides release control and scheduling flexibility | Enables "hands-off" deployment with no human intervention |
| Lower risk tolerance needed | Requires very high confidence in test automation |
| Testing focuses on risk mitigation | Testing must cover expansive use cases |
| Well suited for regulated environments | Better for teams already adept with DevOps |
Let‘s illustrate the contrast with some real-world scenarios:
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A financial services firm uses continuous delivery to release quarterly upgrades after manual user acceptance testing (UAT) and security reviews to satisfy compliance needs.
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An e-commerce site leverages continuous deployment so new features, UI changes, and bug fixes go live as soon as they are developed and pass automated smoke tests to stay competitive.
So in essence, continuous delivery offers more control while continuous deployment emphasizes automation and velocity.
Deciding Which Approach to Use
When should teams utilize continuous delivery versus continuous deployment then? Here are some key factors to weigh:
Release Velocity Needs – If you require frequent small releases to adapt quickly, continuous deployment allows pushing incremental changes constantly. For less frequent releases, delivery may suffice.
Risk Appetite – Releasing untested code could significantly impact users. While risks are mitigated with rigorous automation, continuous deployment still warrants high confidence. Delivery lowers risks since releases require human validation.
Compliance Requirements – Highly regulated environments like healthcare often mandate manual verification and auditing before release. Continuous delivery allows validating changes to meet compliance needs.
Team Maturity – Continuous deployment has more upfront tooling and process complexities. It works better for teams with strong automation, DevOps, and agile experience whereas continuous delivery has a gentler onboarding.
Many teams start with continuous delivery as a stepping stone to deployment, while others maintain delivery if it meets their business needs. Evaluate your own requirements, capabilities, and constraints to determine the right approach.
Best Practices for Implementation
Regardless of which methodology you choose, how do you successfully adopt continuous practices? Here are expert tips:
Start Small – Begin by automating CI builds or testing for one service, not your entire architecture. Slowly expand scope, tooling, and environments.
Rigorously Automate Testing – Comprehensive automated test coverage is vital before rolling out either practice. Prioritize unit, integration, UI, load, security, and accessibility testing.
Standardize Environments – Leverage infrastructure-as-code tools to replicate production environments and avoid release surprises.
Instrument Telemetry – Incorporate thorough monitoring for operational metrics, logs, user behavior analytics, and custom app events.
Right-size Governance – Scale approval processes to balance velocity and oversight without being overly burdensome.
Anchor on Culture – Drive culture shifts via extensive training, coaching, and shared team accountability for outcomes.
Improve Continuously – Keep inspecting processes for bottlenecks, tool gaps, test holes and incrementally address them over time.
In Closing: Start Where You Are
Determining whether continuous delivery or deployment better fits your needs depends on several contextual factors. Hopefully this guide has demystified the core differences and key considerations around adopting each practice.
My recommendation – start where you are right now. The most important step is to begin building competency with continuous integration, test automation, infrastructure as code, and monitoring. These foundations will set you up for success then regardless of which approach best aligns with your risk appetite and velocity requirements in the long run.
The subtle differences between delivery and deployment matter less than committing to maturing your own continuous practices. Through small and frequent iterations, teams can transform and improve how they build, test, and release software to customers. Both end goals offer immense rewards – from accelerating innovation to boosting quality.
So don’t get fixated on which checkbox to mark today. Instead focus on starting the journey now by putting one foot steadily in front of the other. With continuous improvement as your North Star, you’ll inevitably cross the finish line. Good luck!
