Java guide — every framework

Java rate limitingwithout buckets to manage.

Modules for Spring Boot, Jakarta Servlet, and JAX-RS on Maven Central. Each checks the caller’s key, charges their credits, and applies their plan’s rate limit.

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  • Keys issued per customer
  • Credits that refill
  • Limits per plan, not per process

Official SDKs with drop-in middleware for the stack you already run

  • Python
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  • Rust
  • PHP
  • .NET
  • Java
API requests validated
100M+
Average key validation
<5ms
Average analytics ingest
<5ms
Check and log, end to end
<10ms

The usual Java rate limiter counts requests. It doesn’t know your customers.

Java teams use Bucket4j or Resilience4j’s RateLimiter — token buckets in the JVM, with distributed backends to wire up for clusters and no idea of customers or balances.

With Bucket4j or Resilience4jtoday
  • A bucket per customer to create and evict
  • A distributed backend before nodes agree
  • No API keys: issuing, hashing, scoping, and revoking them is still yours to build
  • No credit balance: a request can’t cost 5 on one route and 1 on another, or refill each month
  • One limit for everyone — no per-plan limits for Free, Pro, and Enterprise customers
  • No per-customer usage log to answer “why was I blocked?” or bill against
With ReqKey in Javaone middleware
  • API keys issued per customer, prefixed, hashed, and revocable from the dashboard
  • A credit balance per customer — price each route, refill every hour, day, week, or month
  • Rate limits set per plan, shared by all of a customer’s keys, from 1 second to 24 hours
  • The same count on every worker, instance, and region — no Redis to run
  • Over the limit? A 429 with Retry-After, and no credits charged
  • Every request logged per customer — status, latency, endpoint — in under 5ms
The verdict is a request attribute, ReqKeyAttributes.DECISION. See the code

Java in three steps, one of them code.

ReqKey runs inside your API, not in front of it. Your server asks one question per request and gets an answer in under 5ms.

  1. 1

    Install the SDK

    com.reqkey:reqkey-spring-boot-starter

  2. 2

    Set your project key

    Copy it from the dashboard into REQKEY_PROJECT_KEY. It stays on your server.

  3. 3

    Add the middleware

    Every request is checked, charged, and logged before your handler runs.

application.ymlcom.reqkey:reqkey-spring-boot-starter
# src/main/resources/application.yml
reqkey:
  project-key: ${REQKEY_PROJECT_KEY}
  api-id: api_payments
  key-name: X-Startup-Key
  exclude-paths:
    - /health
 
// ── PaymentsController.java ───────────────────────────────
// The starter registers one filter; the decision is a request attribute.
@PostMapping("/payments")
Map<String, Object> create(HttpServletRequest request) {
    VerificationResult decision = (VerificationResult)
        request.getAttribute(ReqKeyAttributes.DECISION);
    return Map.of("creditsRemaining", decision.getCreditsRemaining());
}
Also in Java: Spring Boot, Jakarta Servlet, JAX-RSFull Java reference

Every request gets one of these answers

  • 200Valid key, credits charged — your handler runs
  • 402Out of credits
  • 403Key disabled, or not allowed on this API
  • 429Over the rate limit — no credits charged

Where ReqKey sits

Your customer
Your APIReqKey, under 5ms
Your handler

Responses go straight back to your customer. ReqKey sees the key check and the log line, nothing else.

Credits

Charge each route what it costs you.

A lookup can cost 1 credit and a render 5, from the same balance. Excluded paths are never validated, charged, or recorded. In Java:

Per-route credits · Java
ReqKeyMiddlewareConfig.builder("api_images")
        // Exact paths or trailing-* prefixes: never validated, charged, or recorded
        .excludePath("/health")
        .excludePath("/docs/*")
        // Or decide per request with a predicate
        .protectWhen(request -> request.getPath().startsWith("/api/"))
        // Charge endpoints differently — a CreditResolver instead of an int
        .credits(request -> request.getMethod().equals("POST") ? 5 : 1)
        .build();

Rate limits

Set limits on plans, not in code.

Your Java code never hard-codes a number. Each plan carries its credits, refill, and rate limit; moving a customer to Pro changes all three with no deploy.

PlanCreditsRate limit
Free1,000 / month5 req / s
Pro50,000 / month50 req / s
Scale1,000,000 / month500 req / s
429Over the limit, a call is answered with Retry-After and costs nothing — no credits and no quota.

Example plans. You name them and pick the numbers.

Notes for Java teams hit in production.

Pick one module

The Spring Boot starter, reqkey-servlet, or reqkey-jaxrs — each pulls in the core client.

Retries you control

Validation is never retried by default, so a customer can’t be charged twice.

Plain client

The core module verifies keys from batch jobs and consumers too.

Java rate limiting: the questions teams ask.

Something else? Ask the team or read the docs.

  • Java 17 or newer. The servlet module targets Jakarta Servlet 6 and the JAX-RS module Jakarta REST 3.1.

  • Quarkus REST is Jakarta REST, so the JAX-RS Feature is the way in.

  • On their plan or on the customer (consumer) in ReqKey — a number of requests per window from 1 second to 24 hours, shared by all of that customer’s keys. Your Java code never hard-codes a limit, so upgrading a customer is a dashboard change, not a deploy.

  • A check averages under 5ms. ReqKey runs inside your app as middleware, not as a gateway in front of it, so responses go straight back to your customer.

  • You choose: fail closed and answer 503, or fail open and let requests through. Invalid keys are denied either way, and a validation is never retried, so no one is charged twice.

Guides for each Java framework.

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