Hello guys, If you are preparing for interviews at High-Frequency Trading (HFT) firms, hedge funds, investment banks, or crypto exchanges, then one thing is guaranteed: You will be asked about low latency systems. Building such systems is a completely different ball game. It’s not just about writing clean code — it's about writing fast code that responds in microseconds. I’ve worked on low-latency Java applications that run in production under tight time constraints, and in this post, I’ll share what I’ve learned in easy Indian English, with some practical examples.
10 Low Latency Tips for Java Developers
Without any further ado, here are the top 10 tips and tricks you can employ to reduce latency in Java applications. These are tried and tested tips and many of them I have seen it working on production on big hedge funds and sell side firms.
Let’s get started.
1. Avoid Garbage Collection (GC) Wherever Possible
Java’s GC is great, but for low-latency apps, even a few milliseconds of pause can cause serious issues — missed trades, delayed orders, or failed market data processing.
Tip: Use Low-Latency Garbage Collectors
Use ZGC or Shenandoah — these are designed to reduce pause times drastically (sub-millisecond).
// Enable ZGC in JVM options
-XX:+UseZGC
These are much better than the old G1GC or CMS in latency-sensitive environments.
2. Use Off-Heap Memory
GC only collects on-heap memory. So, to bypass GC completely, use off-heap memory to store data like tickers, symbols, order books, etc.
Example: Using DirectByteBuffer
ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
buffer.putInt(42);
Off-heap is useful when you want zero GC impact and better control of memory.
3. Optimize for NUMA Awareness
NUMA stands for Non-Uniform Memory Access. Your server might have multiple CPU sockets. Accessing memory from a different socket (remote NUMA node) is 3x slower than accessing local memory.
Tip:
Try to pin threads and memory to the same NUMA node. Use OS tools like numactl or Java libraries that support NUMA-aware thread affinity.
$ numactl --cpunodebind=0 --membind=0 java -jar myapp.jar
4. Warm Up the Application
Java uses JIT (Just-In-Time) compiler to compile bytecode to machine code at runtime. Cold-start apps will be slow initially.
Solution:
Warm up the app before market open. Send expected volume of traffic to your app to trigger JIT optimizations.
public static void warmUp() {
for (int i = 0; i < 1_000_000; i++) {
processTrade("GOOG", 100);
}
}
Run this before real traffic begins.
5. Use Pre-Allocated Buffers (e.g. RingBuffer)
Allocating memory during runtime increases GC pressure. Instead, use pre-allocated structures like RingBuffer.
This idea is used by LMAX Disruptor, a high-performance inter-thread messaging library.
RingBuffer<TradeEvent> ringBuffer = RingBuffer.createSingleProducer(...);
// Use ringBuffer to publish and consume events
No object allocation during runtime = No GC.
6. Use High-Performance Libraries
Some open-source libraries are built specifically for low-latency systems.
Two good options:
Chronicle Queue: High-performance persisted queue (used for market data, order logs).
Aeron: Ultra-fast messaging system (used by trading platforms and exchanges).
ChronicleQueue queue = SingleChronicleQueueBuilder.binary("order-logs").build();
These tools are battle-tested for performance.
7. Scale Horizontally
Sometimes the best way to reduce latency is not to optimize code, but to divide and conquer.
Tip:
Split your systems:
- By symbol range (e.g. A-L handled by one server, M-Z by another).
- By volume (high volume vs low volume instruments).
This allows each process to focus on a smaller workload = faster response.
8. Avoid Common Java Mistakes
Here are some common pitfalls to avoid in low-latency Java systems:
- Avoid synchronized blocks — use lock-free structures instead
- Avoid heavy logging during real-time processing
- Avoid allocating new objects inside tight loops
- Avoid reflection and unnecessary polymorphism
9. Use Busy Waiting for Ultra-Low Latency (Optional)
In cases where you need microsecond-level response, traditional thread blocking (e.g., wait() or sleep()) is not acceptable.
Solution:
Use busy spin with Thread.onSpinWait() (Java 9+):
while (!flag) {
Thread.onSpinWait();
}
Caution: This increases CPU usage — only use in critical parts of the system.
Summary
Here is the summary of all the low latency tips I have shared in this article
Conclusion
That's all about 10 important low latency tips for Java developers. Whether you are working with a low latency app in Java and trying to improve performance of If you’re preparing for HFT interviews, or just want to write fast and efficient Java, these tips will give you a serious edge.
These tricks are not theoretical — they are used in real production systems where every microsecond matters.
Whether it’s stock trading, crypto exchanges, or real-time analytics — low latency is a must.
If you liked this, let me know! I’ll be happy to share more about my experience building ultra-fast Java apps.
Got your own tips? Drop them in the comments — we all learn from each other.
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