Calculating ROI for Java Modernization: Practical Advice from the Trenches
A practical guide for Java architects to assess modernization ROI. Based on real-world experience with greenfield, migration, and cloud-native projects.
When teams ask me about return on investment (ROI) for moving to Quarkus or even just modernizing their Java stack, I always come back to a simple idea: ROI is never just a spreadsheet. It’s about making smart, long-term bets on productivity, efficiency, and the people building your software.
I’ve been through this process a few times, both for greenfield projects and complex brownfield migrations. So instead of offering generic theory, let me share what I’ve learned to help guide your own ROI discussions. Especially if you're weighing Quarkus against more traditional Java stacks like Spring or Jakarta EE.
ROI Basics: What Are We Actually Measuring?
At its core, ROI = (Benefits − Costs) / Costs
For software, that breaks down into:
Development costs (time, skills, training)
Operational costs (cloud bills, infrastructure, licensing)
Productivity gains (or losses)
Impact on revenue, uptime, and end-user satisfaction
Let’s walk through four common scenarios and how I’ve approached them.
Greenfield: Choosing Between Quarkus and Spring
Starting from scratch? That’s a good place to optimize early.
If your team already knows Spring, the short-term ROI might seem better there. But in the long run, I’ve seen Quarkus projects deliver greater operational efficiency and faster feedback loops, especially in Kubernetes or cloud-native environments.
What I’ve seen with Quarkus:
Sub-second startup means we don’t need to over-provision for peak traffic anymore—great for autoscaling or serverless.
Live coding and dev services shave off hours from the inner dev loop.
Native executables slash memory and CPU usage. In one case, we fit double the number of services on the same nodes.
Cloud-native support out of the box: no need to duct-tape YAML files and annotations later.
What Spring still offers:
A deep, mature ecosystem.
Lots of tutorials and libraries.
A massive pool of developers already trained on it.
Advice: For greenfield, compare long-term operational cost and time-to-market, not just initial team familiarity. And don’t underestimate the morale boost from faster feedback cycles and fewer dev headaches.
Brownfield: Migrating Spring to Quarkus
This is where ROI gets tricky and where I’ve learned to be brutally honest about effort vs. payoff.
Migration has a cost: analyzing the codebase, mapping unsupported features, rewriting layers, re-validating tests, training the team.
But the payoff can be dramatic. In one project, moving a microservice fleet to Quarkus cut a monthly cloud spend by double digit percentages due to reduced memory and CPU use alone.
Add to that:
Faster cold starts (critical for failover and scaling).
Simplified ops on Kubernetes.
Future-proofing with reactive and native-ready architecture.
Yes, Quarkus provides Spring compatibility layers, but they’re not meant as permanent crutches. Use them to ease the transition, not to avoid it.
Advice: Run a pilot. Pick a non-critical service, migrate it, and measure memory, CPU, response times, and team feedback. That gives you real data, not just a slide deck guess.
Java EE on Kubernetes: Is It Time to Migrate?
If you’ve got traditional Java EE workloads running on Kubernetes, you’re already in a hybrid world with modern ops and legacy runtimes.
This is where Quarkus has been a strong ally in my experience:
Java EE & Jakarta APIs mean familiar code for your team.
Native support trims pod sizes drastically with often halving memory requests.
Rolling updates and health checks get faster and more predictable.
You finally say goodbye to bloated app servers and license costs.
We’ve seen modernized monoliths, broken down into Quarkus services. It was a heavy lift but the operational simplicity and CI/CD speed afterward were worth every sprint.
Advice: Use Quarkus to bring Java EE teams into the cloud-native world without throwing away their expertise. That’s often faster and cheaper than a full replatform.
Jakarta EE Already? Still Consider Quarkus
If you’ve already migrated from Java EE to Jakarta EE, good news: the API alignment means migrating to Quarkus is often straightforward.
Even so, I’d still run the numbers:
You get build-time optimizations Quarkus is famous for.
Native compilation and reduced memory/cpu demand still bring savings.
Dev mode and dev services make local testing and onboarding a breeze.
Licensing vs. Support Cost
This is less about massive cost savings, and more about optimizing performance and developer experience.
Advice: Use this migration to double down on automation, CI/CD, and modern dev practices. Quarkus encourages that shift by design.
Productivity: The Hidden ROI Multiplier
Honestly, this is where I think Quarkus shines the most and it’s also the hardest to quantify.
What boosts productivity in Quarkus:
Dev mode hot reload is instant. No more waiting for builds.
Dev Services auto-provision dependencies. Less config, more code.
Native build speed keeps improving, and CI gets faster.
Sure, Spring has Spring Boot Devtools, massive community help, and fantastic IDE support. But for teams building cloud-native apps today, Quarkus feels more aligned with how they work.
Advice: Survey your team. Track time spent on local setup, testing, builds, and onboarding. Those minutes per developer add up quickly over months.
A Final Thought on TCO
ROI isn’t just about what saves money today. It’s about:
Reducing future rework.
Avoiding lock-in to outdated tech.
Attracting developers who want to work with modern tools.
Scaling systems with less hardware and fewer surprises.
Yes, Spring might still make sense for some teams. But if you’re aiming for Kubernetes-native, performance-sensitive, or fast-moving dev teams, Quarkus is absolutely worth the time to evaluate seriously.
If you’re in the middle of evaluating frameworks, or just want to justify an architectural investment feel free to steal this mental model. It’s worked for me across multiple orgs and project sizes.
And whatever you choose, just make sure your ROI doesn’t stop at the data center. The best returns often start with the people building the software.
Want more on Quarkus modernization strategies or real-world migration stories? You can find me over at https://quarkus.io/userstories/