Welcome to Özkan Pakdil’s Blog

Have you ever wondered exactly which files are being hammered by your Linux system in real-time? While tools like iotop or lsof are great, sometimes you want something more visual, custom, and lightweight. In this post, I’ll walk you through how I built a Real-time File I/O Heatmap using the power of eBPF for data collection and Java 25 for a modern Terminal UI (TUI). What is eBPF and Why Use It? eBPF (Extended Berkeley Packet Filter) is a revolutionary technology that allows you to run sandboxed programs in the Linux kernel without changing kernel source code or loading kernel modules. ...

Introduction Today I’m excited to announce the addition of Bun to our microservice framework benchmark suite. The results are nothing short of remarkable . Bun has proven to be one of the fastest runtimes in our entire test suite, competing directly with Rust frameworks! What is Bun? Bun is a modern JavaScript runtime built from scratch using Zig and JavaScriptCore (the engine that powers Safari). It’s designed to be a drop-in replacement for Node.js with a focus on: ...

The Spark The other day I came across a fascinating post on Substack by Skilled Coder about Java data structure performance. The post showed some eye-opening numbers for 10M operations: Get operations: HashMap.get() → ~140 ms TreeMap.get() → ~420 ms ArrayList.get(i) → ~40 ms LinkedList.get(i) → ~2.5 s Insertion (10M elements): ArrayList.add() → ~180 ms HashMap.put() → ~300 ms LinkedList.add() → ~900 ms This got me thinking: how do these numbers compare to Eclipse Collections? And more importantly, how can we calculate these numbers ourselves using open source tools? ...

Why this post I started this mini‑project after seeing a common roadblock: PKIX path building failed when calling HTTPS services with OpenFeign. The goal was to create a tiny, runnable example that eliminates guesswork, shows how to configure client certificates and trust properly, and layers basic IAM policies on top. Reference: https://stackoverflow.com/questions/79835509/unable-to-configure-ssl-context-for-open-feign-client-getting-pkix-error What’s inside the example Two Spring Boot apps: Server: HTTPS on 8443, requires client certs (mTLS), and recognizes/authorizes callers with Spring Security’s X.509 support. Client: Spring Cloud OpenFeign calling the server via Apache HttpClient5 with a custom SSLContext. A one‑command cert toolchain (local CA → server/client certs → PKCS#12 keystores/truststores). An automated test script that runs a positive call (expected 200) and a negative call with an unauthorized client (expected 403). Project (ready to publish here): ...

Introduction Test results for this benchmark run → Over the last two days, I’ve expanded our microservice framework benchmark suite to include two new contenders: Golang and Express.js. This addition allows us to compare performance across a broader spectrum of technologies, from compiled languages like Rust and Go to JVM-based frameworks and Node.js. New Additions Golang (Go 1.24.10) Go was added using the standard library only - no external frameworks. The implementation uses net/http package which is known for its excellent performance and simplicity. ...