Quarkus vs Spring Boot — A Practical Comparison for 2026

The Question — Which Framework?

If you’re starting a new Java microservice in 2026, you’ve got a genuine choice to make. Spring Boot has been the default for a decade. Quarkus arrived as the “Kubernetes-native” alternative and has matured rapidly. Both target Java 21, both support GraalVM native images, and both have strong communities.

This isn’t a “which is better” post — it’s a “when to choose which” post, backed by code you can compare side by side.

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Architecture Differences

The fundamental philosophical difference: when work happens.

flowchart LR
    subgraph Spring Boot
        direction TB
        S1[Application Starts] --> S2[Classpath Scanning]
        S2 --> S3[Bean Discovery]
        S3 --> S4[Proxy Generation]
        S4 --> S5[Dependency Injection]
        S5 --> S6[Ready to Serve]
    end

    subgraph Quarkus
        direction TB
        Q1[Build Time] --> Q2[Classpath Scanning]
        Q2 --> Q3[Bean Discovery]
        Q3 --> Q4[Bytecode Generation]
        Q4 --> Q5[Runtime Start]
        Q5 --> Q6[Minimal DI Wiring]
        Q6 --> Q7[Ready to Serve]
    end

Spring Boot does most of its heavy lifting at runtime — scanning, proxy generation, condition evaluation. Quarkus moves as much as possible to build time using its extension framework. The result: dramatically faster startup and lower memory at the cost of longer builds.

Aspect	Spring Boot	Quarkus
DI resolution	Runtime	Build time
Configuration	Runtime conditions	Build-time augmentation
Proxy generation	Runtime (CGLIB/JDK)	Build time (bytecode)
Reflection	Heavy use	Minimized (records metadata at build)
Hot reload	Spring DevTools (restart)	Quarkus Dev Mode (instant)

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Side-by-Side Code

Let’s build the same simple REST API in both frameworks: a BookController with CRUD operations.

REST Endpoint

Spring Boot:

@RestController
@RequestMapping("/api/books")
public class BookController {

    private final BookService bookService;

    public BookController(BookService bookService) {
        this.bookService = bookService;
    }

    @GetMapping
    public List<Book> findAll() {
        return bookService.findAll();
    }

    @GetMapping("/{id}")
    public ResponseEntity<Book> findById(@PathVariable Long id) {
        return bookService.findById(id)
                .map(ResponseEntity::ok)
                .orElse(ResponseEntity.notFound().build());
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public Book create(@Valid @RequestBody Book book) {
        return bookService.save(book);
    }
}

Quarkus:

@Path("/api/books")
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public class BookResource {

    private final BookService bookService;

    @Inject
    public BookResource(BookService bookService) {
        this.bookService = bookService;
    }

    @GET
    public List<Book> findAll() {
        return bookService.findAll();
    }

    @GET
    @Path("/{id}")
    public Response findById(@PathParam("id") Long id) {
        return bookService.findById(id)
                .map(book -> Response.ok(book).build())
                .orElse(Response.status(Status.NOT_FOUND).build());
    }

    @POST
    public Response create(@Valid Book book) {
        Book created = bookService.save(book);
        return Response.status(Status.CREATED).entity(created).build();
    }
}

Dependency Injection

Spring Boot:

@Service
public class BookService {

    private final BookRepository bookRepository;

    public BookService(BookRepository bookRepository) {
        this.bookRepository = bookRepository;
    }

    // constructor injection — no annotation needed (single constructor)
}

Quarkus:

@ApplicationScoped
public class BookService {

    private final BookRepository bookRepository;

    @Inject
    public BookService(BookRepository bookRepository) {
        this.bookRepository = bookRepository;
    }

    // CDI-based — @Inject required on constructor
}

Configuration

Spring Boot (application.yml):

spring:
  datasource:
    url: jdbc:postgresql://localhost:5432/books
    username: ${DB_USER:postgres}
    password: ${DB_PASS:secret}
  jpa:
    hibernate:
      ddl-auto: validate

Quarkus (application.properties):

quarkus.datasource.db-kind=postgresql
quarkus.datasource.jdbc.url=jdbc:postgresql://localhost:5432/books
quarkus.datasource.username=${DB_USER:postgres}
quarkus.datasource.password=${DB_PASS:secret}
quarkus.hibernate-orm.database.generation=validate

Data Access

Spring Boot (Spring Data JPA):

public interface BookRepository extends JpaRepository<Book, Long> {
    List<Book> findByAuthor(String author);
}

Quarkus (Panache):

@ApplicationScoped
public class BookRepository implements PanacheRepository<Book> {
    public List<Book> findByAuthor(String author) {
        return find("author", author).list();
    }
}

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Performance Benchmarks

Tested on: Apple M3 Pro, 18GB RAM, Java 21.0.3, Spring Boot 3.5.0, Quarkus 3.16.0

Metric	Spring Boot (JVM)	Spring Boot (Native)	Quarkus (JVM)	Quarkus (Native)
Startup time	2.1s	0.08s	0.9s	0.02s
RSS memory (idle)	280 MB	72 MB	145 MB	32 MB
RSS memory (load)	420 MB	148 MB	230 MB	78 MB
Throughput (req/s)	48,200	42,800	47,500	41,200
Build time	8s	3m 20s	12s	2m 45s
JAR size	42 MB	N/A	38 MB	N/A
Native binary size	N/A	98 MB	N/A	72 MB

Key takeaways:

• JVM throughput is comparable — the performance difference is mostly startup + memory.
• Native images trade throughput for startup/memory — JIT optimizes better over time.
• Quarkus native compiles faster — less reflection to configure.

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Developer Experience

Feature	Spring Boot	Quarkus
Hot reload	DevTools (restarts JVM, ~2s)	Dev Mode (instant, no restart)
IDE support	Excellent (IntelliJ, Eclipse)	Good (IntelliJ plugin improving)
Documentation	Extensive, mature	Good, well-organized
Stack Overflow answers	Very high	Growing
Testing	@SpringBootTest, Testcontainers	@QuarkusTest, Dev Services
Dev Services (auto-DB)	Spring Boot 3.1+ Docker Compose	Built-in since Quarkus 2.0
CLI tool	Spring Initializr (web)	quarkus CLI (powerful)
Continuous testing	Separate (IDE/CI)	Built into Dev Mode
OpenAPI generation	SpringDoc (add-on)	Built-in extension

The developer experience gap has narrowed significantly. Quarkus Dev Mode still leads for inner-loop speed. Spring Boot’s ecosystem maturity still wins for “I need a library for X.”

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Ecosystem & Libraries

Need	Spring Boot	Quarkus
REST clients	RestClient, WebClient, Feign	REST Client (MicroProfile), Vert.x
Messaging	Spring Kafka, Spring AMQP	SmallRye Reactive Messaging
Security	Spring Security	Quarkus Security, Keycloak
GraphQL	Spring for GraphQL	SmallRye GraphQL
gRPC	grpc-spring-boot-starter	quarkus-grpc
Scheduling	@Scheduled	@Scheduled (quarkus-scheduler)
Caching	Spring Cache + any provider	quarkus-cache (Caffeine)
Health checks	Actuator	SmallRye Health
Metrics	Micrometer	Micrometer (via Quarkus extension)
Observability	Micrometer Tracing	OpenTelemetry (first-class)

Spring Boot wins on breadth — if a Java library exists, there’s probably a Spring integration. Quarkus wins on coherent defaults — extensions are designed to work together with minimal configuration.

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Native Compilation

Spring Boot with Spring AOT

# Build native image
./mvnw -Pnative native:compile

# Or with Buildpacks (no local GraalVM needed)
./mvnw spring-boot:build-image -Dspring-boot.build-image.imageName=myapp:native

Spring AOT processes @Conditional annotations at build time and generates reflection configuration. You may still need reflect-config.json for libraries that use reflection heavily.

Quarkus Native

# Build native image
./mvnw package -Dnative

# With container build (no local GraalVM needed)
./mvnw package -Dnative -Dquarkus.native.container-build=true

Quarkus was designed for native from day one. Extensions register reflection automatically. You rarely need manual configuration.

Comparison

Aspect	Spring Native	Quarkus Native
Configuration effort	Medium (improving)	Low
Library compatibility	~90% of Spring ecosystem	Extensions are native-ready
Build time	Longer (more reflection to process)	Shorter
Runtime performance	Good	Good
Debugging native issues	Harder	Easier (better error messages)

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When to Choose Which

flowchart TD
    A[New Java Microservice] --> B{Team's Spring experience?}
    B -->|Deep| C{Startup/memory critical?}
    B -->|Minimal or none| D{Scale to zero needed?}
    
    C -->|Yes - serverless/edge| E[Quarkus Native]
    C -->|No - long-running| F[Spring Boot JVM]
    
    D -->|Yes| E
    D -->|No| G{Large ecosystem needs?}
    
    G -->|Complex integrations| F
    G -->|Standard patterns| H[Quarkus JVM]

Decision Matrix

Scenario	Recommendation	Why
Enterprise with Spring teams	Spring Boot	Leverage existing expertise
Serverless / AWS Lambda	Quarkus Native	Fastest cold start
Kubernetes scale-to-zero	Quarkus Native	Memory + startup
Long-running monolith	Spring Boot	Ecosystem, JIT optimization
New team, greenfield	Either (evaluate both)	Both are excellent
Event-driven reactive	Quarkus	Vert.x integration, SmallRye
Complex security requirements	Spring Boot	Spring Security maturity
CLI / short-lived processes	Quarkus Native	Sub-second startup

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Can They Coexist?

Yes. In a microservices architecture, there’s no rule that says every service must use the same framework. A practical pattern:

flowchart LR
    subgraph Services
        A[API Gateway<br>Spring Boot] --> B[User Service<br>Spring Boot]
        A --> C[Notification Service<br>Quarkus Native]
        A --> D[Pricing Engine<br>Quarkus JVM]
        A --> E[Reporting Service<br>Spring Boot]
    end
    
    subgraph Shared
        F[Kafka]
        G[PostgreSQL]
        H[Redis]
    end
    
    B --> F
    C --> F
    D --> G
    E --> G
    B --> H

Guidelines for coexistence:

• Use language-agnostic communication (REST, gRPC, Kafka) — not framework-specific.
• Shared libraries should be plain Java (no Spring/CDI annotations).
• Standardize on OpenTelemetry for observability across both.
• Use the same build pipeline (Maven/Gradle) — both frameworks support both.

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References

• Quarkus — Guides
• Spring Boot — Reference Documentation
• GraalVM Native Image
• Quarkus vs Spring Boot — Red Hat Developer
• Spring AOT Documentation
• MicroProfile Specification