Runtime Config Hot-Swap for Java

How it works

Three steps. Zero restarts.

Annotate

Add @Marz to any field — boolean, int, long, double, or String. Point it at your config file.

Edit config

Change the value in your YAML, JSON, or properties file. The WatchService detects the change in milliseconds — on local files, Docker volumes, and Kubernetes ConfigMaps.

Value updates

The field swaps in ~50ms. Next read sees the new value. No restart, no proxy, no bean rebuild.

The code

One annotation. That's the entire API.

@Service
public class CheckoutService {

    @Marz(key = "feature.checkout.enabled",
          source = "file://config/features.yml")
    private volatile boolean newCheckoutEnabled = false;

    // Edit the YAML → field updates in ~50ms
    // No restart. No proxy. No @RefreshScope. Just volatile.
}

Add to your project

<dependency>
    <groupId>com.mymarz</groupId>
    <artifactId>marz-spring-boot-starter</artifactId>
    <version>0.1.0</version>
</dependency>

Why MARZ

Honest comparison

	MARZ	@RefreshScope	Rolling Restart	LaunchDarkly
Config change speed	~50ms	2-10s (bean rebuild)	15-45 min	~200ms (network)
Read performance	~31ns (volatile)	~50ns (CGLIB proxy)	~31ns (after restart)	~1ms (SDK call)
Requires restart	No	No (but rebuilds beans)	Yes	No
Infrastructure needed	None	Config Server + Bus	CI/CD pipeline	SaaS dependency
Granularity	Field-level	Bean-level	Full app	Flag-level
Cost	Free (OSS)	Free	DevOps time	$20K-$120K/yr

~31ns read latency Measured volatile read. Zero IO. Zero proxy.

~50ms swap time WatchService detects change. Volatile field swaps value.

0 restarts Ever. That's the point.

Benchmark

1,000,000 reads, head-to-head.

	@Marz	Naive file re-read
Total time (1M reads)	~32 ms	~36.5 s
Read latency	31 ns/op	36,461 ns/op
Throughput	32.3M ops/s	27.4K ops/s
Read-path disk I/O	0 bytes	~2.03 GB

1,176× faster read path

100% read-path I/O eliminated

Representative benchmark — 1M reads per strategy on Java 17, Apple Silicon. Exact figures vary by machine & JVM warmup; the CI test asserts a conservative ≥5× floor. The naive baseline re-opens and re-parses the file on every read; @Marz reads a volatile field and touches disk only when the file actually changes.

Ready to stop restarting?

Add the Maven dependency. Annotate a field. Edit your config. You'll have runtime hot-swap in under 60 seconds.

Read the quickstart Star on GitHub

CONTROL