Vicedomini Softworks

Software Development

Spring Boot vs Quarkus: Choosing a Java Framework

5 November 2026

Engineer comparing Spring Boot and Quarkus builds

Spring Boot is the safer default when a team already knows Spring and depends on its wide ecosystem, while Quarkus is the stronger choice when startup time, memory footprint and Kubernetes-native behaviour drive the cost or the architecture. Both are mature, production-grade Java frameworks. The decision rarely turns on which is “better” in the abstract: it turns on the deployment model, the existing skills of the team, the libraries the application needs and the support horizon the organisation requires.

This comparison sets out the architectural difference that explains most of the numbers, what the published benchmarks do and do not show, how each framework behaves on Kubernetes and OpenShift, what migration involves, and a practical method for deciding.

Vicedomini Softworks
Choose the Right Java Foundation
Vicedomini Softworks builds custom Java software with Spring Boot and Quarkus, helping organizations align framework decisions with their technical and business needs.
Ask for a consultation

TL;DR

  • Spring Boot performs much of its work at runtime and offers the broadest ecosystem; Quarkus moves work to build time, which yields faster startup and lower memory use.
  • In the Quarkus team’s own 2026 benchmark, Quarkus reached 2.7 times the transaction throughput of Spring Boot, started 2.3 times faster and used about half the memory. Treat vendor figures as a hypothesis to confirm on your own workload.
  • Quarkus is Kubernetes-native by design; Spring Boot reaches comparable integration through Spring Cloud Kubernetes and Actuator.
  • Teams with Spring expertise can adopt Quarkus incrementally through its Spring compatibility extensions rather than rewriting.
  • A two-week pilot on one stateless service with variable traffic is a sound way to decide with evidence.

Table of Contents

The architectural difference that explains most of the comparison

Spring Boot builds on the Spring Framework, whose strength is a very large, mature programming model. Much of the wiring, such as classpath scanning, bean creation and proxy generation, happens when the application starts. This runtime flexibility is the reason the ecosystem is so broad, and it is also the reason a conventional Spring Boot service on the JVM takes longer to start and holds more memory than a leaner alternative. The summary offered in a 2026 practical comparison puts it plainly: Spring Boot does most of its heavy lifting at runtime, whereas Quarkus shifts that work to build time.

Quarkus performs dependency injection resolution, configuration processing and much of the framework initialisation during the build. The result is an application that has less to do when it launches and keeps fewer framework structures in memory. Quarkus also has a reactive core, so a single application may use imperative code, reactive code or both, as the Quarkus team describes.

Spring Boot has narrowed the gap, and it now supports ahead-of-time processing and native images as well. The structural point remains: Quarkus was designed around build-time optimisation and container workloads from the start, while Spring Boot extends a runtime-oriented model towards them.

Startup time, memory and throughput

The figures most often quoted come from the Quarkus project itself, which is worth stating before reading them. In the Quarkus team’s 2026 benchmark, Quarkus handled 2.7 times more transactions per second than Spring Boot, started 2.3 times faster and used half the memory. A related Quarkus Insights episode reports idle memory of 88 MB for Quarkus against 204 MB for Spring Boot, and peaks under load of 412 MB against 827 MB.

Spring Boot and Quarkus benchmark comparison

The same source links memory to garbage collection: a larger heap leads to more aggressive collection and a higher resource cost in comparable cloud deployments. For an organisation running dozens of replicas, memory per instance is a direct line on the infrastructure bill, which is why these numbers matter more in microservice estates than in a single monolith.

A few cautions keep the comparison honest:

Factor Spring Boot Quarkus
Where framework work happens Mostly at runtime Mostly at build time
Startup on the JVM Slower Faster
Memory footprint Larger Smaller
Native image Supported through AOT processing Core design goal
Programming model Imperative, with reactive options Imperative, reactive or both
Ecosystem breadth Very broad Broad and growing

Benchmarks depend on hardware, payload, database access and warm-up. One independent 2026 blog test ran on a 2-vCPU container without a database and over only 15 seconds, and its author states that it cannot establish long-run behaviour. A service dominated by database latency will see a smaller difference than a service that is CPU-bound or that scales to zero and restarts often. The sensible reading is directional: Quarkus tends to be leaner, and the size of the advantage should be measured on the actual workload.

Kubernetes, OpenShift and microservices

Both frameworks run well in containers, but they approach the platform differently.

Quarkus can generate Kubernetes, OpenShift and Knative resources, apply them to a cluster and, with a container-image extension such as Jib, build and push the image, as its Kubernetes extension guide documents. Its Kubernetes-native page describes single-step microservice deployment, OpenTelemetry tracing, SmallRye Health for health decisions, and ConfigMaps and Secrets as configuration sources. Fast startup and low memory also make Quarkus a natural fit for serverless and scale-to-zero patterns.

Spring Boot reaches the same destination through its own components. Spring Cloud Kubernetes lets applications use a Kubernetes DiscoveryClient to query services and endpoints by name, and ConfigMaps and Secrets can externalise configuration, with observed ConfigMap changes able to trigger a reload of beans or the Spring context. On the operations side, Spring Boot’s Actuator provides availability health endpoints usable as probes, together with metrics, Prometheus export and startup-time metrics.

In practice, Spring Boot on Kubernetes is entirely viable and well understood, particularly where a platform team has already standardised on Spring Cloud. Quarkus offers a more coherent set of Kubernetes-oriented defaults out of the box, which reduces the amount of assembly required. The comparison of ecosystem breadth against Kubernetes-optimised defaults captures the trade-off well.

Ecosystem, skills and developer experience

The ecosystem is where Spring Boot is hardest to displace. Decades of libraries, integrations, documentation, hiring pools and institutional knowledge sit behind it. For a project that needs a specific, less common integration, a Spring starter is more likely to exist already. This breadth is the central reason many enterprises keep Spring as the default.

Quarkus narrows the practical gap for Spring teams. It states that its Spring compatibility extensions support familiar annotations and APIs such as @RestController, @Autowired and JpaRepository, so substantial application code can be reused while the runtime changes. Quarkus is also built on Jakarta EE standards and MicroProfile specifications, which suits organisations that value standards-based portability, and a developer experience built around live coding and a built-in development mode shortens the feedback loop.

The cost of a switch is not zero. A team fluent in Spring will spend some time learning Quarkus idioms such as CDI, Jakarta REST and Panache, and any library without a Quarkus extension needs verification before commitment. That learning investment is usually modest for engineers who already understand dependency injection and REST design, but it should appear in the plan.

Support horizon and enterprise risk

For regulated industries, the framework’s release cadence and support model can outweigh performance. Community release windows are short, and the analysis of enterprise Java supply chains argues that organisations needing multi-year support cycles should look at formal support subscriptions from vendors rather than rely on community builds alone.

On the Quarkus side, Red Hat publishes a life cycle policy for its build of Quarkus: a major version carries full and maintenance support for a minimum of three years, and the product’s minor versions are based on community LTS releases. Spring also has commercial support options. Whichever route is chosen, the support contract and upgrade policy should be agreed before the first production release, not discovered during an incident.

Migrating from Spring Boot to Quarkus

Migration is a engineering project, not a dependency swap. The Quarkus migration guide describes two paths: keep the Spring compatibility extensions for minimal code change, or move to native Quarkus APIs such as Jakarta REST, CDI and Panache for the fullest benefit. It also states that migration can be incremental instead of an all-at-once rewrite.

A Red Hat engineering write-up on migrating a Spring Boot microservices application reaches a consistent conclusion: confirm that the Spring features and libraries in use are supported, expect to replace dependencies and adjust annotations and code, and note that microservices migrate more easily than monoliths.

A sensible sequence follows from this:

Stage Objective Output
Inventory List Spring modules, starters and third-party libraries in use Compatibility matrix
Pilot Migrate one stateless service with variable traffic Measured baseline comparison
Compatibility layer Reuse annotations through the Spring extensions Running service with minimal change
Convergence Move to native Quarkus APIs where it pays off Reduced technical debt
Rollout Migrate remaining services by priority Incremental production adoption

The pilot deserves emphasis. Alex Diniș, in the Quarkus Insights episode cited above, recommends a two-week pilot on a single stateless service with variable traffic, comparing its metrics with the existing baseline. It produces local evidence and limits risk.

When each framework fits

Spring Boot is the stronger fit when the team is deeply invested in Spring, when the application depends on a broad set of Spring projects, when hiring speed matters more than runtime efficiency, or when a monolith or a modest number of long-running services makes startup and memory differences financially marginal.

When each framework fits

Quarkus is the stronger fit when the estate is a large number of containerised microservices on Kubernetes or OpenShift, when workloads scale to zero or burst frequently, when infrastructure cost per replica is a visible budget line, when native compilation is a goal, or when the organisation prefers Jakarta EE and MicroProfile standards.

A mixed estate is a legitimate outcome. A company can keep Spring Boot for established systems and use Quarkus for new cloud-native services, provided the shared concerns of authentication, observability and API contracts are standardised at the platform level rather than inside either framework.

Our perspective

We build with both Spring Boot and Quarkus, and we do not treat the choice as a matter of allegiance. Our stack covers Java, Jakarta EE, Spring Boot and Quarkus, alongside REST and GraphQL APIs, message-driven architectures and cloud-native delivery on Red Hat OpenShift, so the recommendation we write down follows the client’s constraints and not a preferred product.

In our experience the expensive mistakes are rarely about framework speed. They come from choosing a stack without an inventory of the integrations it must support, from migrating a monolith as if it were a microservice, and from skipping a measured pilot. Because clients work directly with the engineers who design and maintain the system, the trade-offs are discussed by the people who will live with the result, and every consulting engagement ends with a written recommendation.

Where services are containerised, bursty and numerous, we lean towards Quarkus and an incremental migration that keeps Spring compatibility in place at first. Where the organisation’s strength is Spring and the ecosystem it needs is there, we say so and keep Spring Boot. Either way, the decision should be backed by code audit findings and by measurements on your own workload.

Pepe F.

Getting an independent recommendation

If the decision affects several services or a migration budget, an outside architectural review is often cheaper than a wrong commitment. Vicedomini Softworks is an Italian software engineering company that serves organisations across EMEA and North America, with no vendor bias and a written recommendation for every consulting engagement. Our architecture and technology stack, code audit and custom development services cover stack selection, technical debt assessment and the implementation of the framework you choose.

Vicedomini Softworks

For organisations without a senior technical leader, our CTO advisory subscriptions are published as follows: CTO Advisory from €1,800 per month, Fractional CTO from €4,000 per month and CTO Partner from €7,500 per month, with an initial assessment from €3,500 as a one-off. Framework selection and migration roadmaps fit naturally within that scope.

FAQ

Is Quarkus faster than Spring Boot?

In the Quarkus team’s 2026 benchmark, Quarkus started 2.3 times faster and handled 2.7 times more transactions per second. Those are vendor-published results under specific conditions, so confirm the difference on your own service. The gap is typically largest for startup-sensitive and memory-constrained deployments.

Is Spring Boot still relevant?

Yes. Its ecosystem, documentation and talent pool remain the largest in the Java world, and it supports ahead-of-time processing and native images. It remains a sound default for teams with Spring experience and for applications that rely on the wider Spring projects.

Can a Spring team move to Quarkus without a rewrite?

Often, in stages. Quarkus provides Spring compatibility extensions for familiar annotations such as @RestController and @Autowired, and its migration guide describes an incremental path. Check each library in use for support first, and begin with a stateless microservice.

Which is better for Kubernetes and OpenShift?

Both run well. Quarkus generates Kubernetes and OpenShift resources directly and has Kubernetes-oriented defaults, while Spring Boot relies on Spring Cloud Kubernetes and Actuator. Teams on OpenShift often find Quarkus a natural fit, though an established Spring platform is equally workable.

Sources

This article was produced with AI assistance and reviewed for accuracy. It is provided for general information only and is not professional advice.

Tell us about your project