Migrating High-Throughput Redirector Service to Quarkus + JDK 25: Virtual Threads & Pinning Concerns

[KarthiSM]

Context:
Modernizing a critical traffic routing service (millions of requests/day) from Spring 5.3.20 + Jetty 9.4.58 + Java 8 to Quarkus + JDK 25 for virtual thread benefits.
Current Architecture:

• Thread-per-request model (200-500 threads under load)
• JAX-RS/Jersey 2.19, Cassandra 3.3.0 (sync), Zookeeper
• Heavy JAXB usage (323 files with @XmlRootElement)
• Custom Spring scopes (AppScope, ScriptScope) for per-tenant beans
• Sub-100ms response time SLA
  Key Questions:

1. JDK 25 Class Loading Pinning
   Saw the GitHub discussion (JDK 25 Support? When? #50130) mentioning "problematic pinning when loading classes" with virtual threads.

• Is this fixed in Quarkus 3.8.*?
• Should we use junit-virtual-threads testing framework to validate?

2. Cassandra Driver Compatibility

• Should we upgrade from Cassandra driver 3.3.0 (sync) to 4.x before Quarkus migration?
• Does quarkus-cassandra-client work well with virtual threads on JDK 25?

3. Custom Spring Scopes → Quarkus CDI
   Our biggest blocker: Custom Spring scopes for per-application bean lifecycle.
   @component
   @scope(AppScope.APP_SCOPE) // No Quarkus equivalent?
   public class ApplicationRulesCache { }

• What's the CDI alternative? Custom extensions? Redesign needed?

4. JAXB + Native Image

• Will quarkus-resteasy-jaxb work out-of-the-box for JVM mode?
• For native: how painful is @RegisterForReflection for 323 JAXB classes?

5. Migration Path
   Which sequence is recommended?

• A) Java 8 → 17 LTS → Quarkus on 17 → JDK 25
• B) Java 8 → 21 LTS → Quarkus on 21 → JDK 25
• C) Java 8 → Quarkus on 17 → JDK 25

6. Production Readiness

• What's the maturity of Quarkus + JDK 25 today?
• Any known issues with UBI9 OpenJDK 25 images (ubi9/openjdk-25:1.24)?
• Performance expectations: thread count 500 → ?, memory savings?

Our Plan:

1. Java 8 → 21 LTS
2. Quarkus POC (simple module first)
3. Virtual thread validation
4. Redesign custom scopes
5. Full migration to Quarkus on Java 25 LTS

Does this make sense?

Looking for: Real-world Spring→Quarkus migration experiences, JDK 25 stability insights, custom scope patterns, virtual thread pinning war stories.
Tags: #quarkus #jdk25 #virtual-threads #spring-migration #production

[cescoffier]

I would not switch to Quarkus 3.8, it's very old. Use 3.33.x (latest LTS).
For virtual threads, I heavily recommend at least Java 25, don't use Java 21, lots of issues have been fixed between 21 and 25.

[nhanth87]

I'm in very high event - driven service (based akka, sbb, jainslee design). if you looking into 10 mil tps (1 - 100 Gbps) then take a look https://github.com/nhanth87/jain-slee
note that it's double license, so don't cheat