Özkan Pakdil Software Engineer

Paint, a lightweight image editor for quick edits

Why I built Paint Whenever I wanted to make a very small edit on my Debian laptop, crop a screenshot, add a quick arrow, or block out a small area, the system only had GIMP for editing images. Powerful, but heavy and slow for tiny, frequent tasks. I wanted something nimble: quick to open, easy to use, and focused on the common one-off edits people do dozens of times a day. ...

Comparison functional code vs imperative code

Java imperative vs functional in 2025 - revisiting a 2015 microbenchmark

Quick numbers (avg; smaller is faster) I (imperative nested): 3.28 µs I2 (imperative freq-map): 1.93 µs F (streams grouping): 127.37 µs FP (parallel streams grouping): 599.28 µs Winner: I2 - imperative freq-map Note: These are sample numbers from the run below on my machine; yours will differ. I/F labels mirror the 2015 post for a simple visual compare. == 2015-style harness (I:/F: lines) == ozkan@ozkan-debian:~/projects/ozkanpakdil.github.io/scripts/compare-2015-25$ ./run.sh javac 25 I:5372 F:22032373 I:5816 F:186352 F:144816 F:134903 F:107685 I:4919 I:4903 I:4698 I:4147 F:104857 == 2025 benchmark summary (fastest → slowest) == ...

Diagnosing a slow Windows Forms screen by adding a missing SQL index

The First Production Performance Problem I Faced (and How I Solved It)

In 2004, I was a new math graduate(Junior Dev) working on an in‑house CRM that was evolving into an ERP. It was a Windows Forms application built with VB.NET and SQL Server (think .NET Framework 1.0/1.1 days - Or we were using that version). One day, a form field became painfully slow. The screen generated a mandate_id that could later become an order_id. The ID was created automatically in the database-an auto-increment primary key plus a few validation checks. Unfortunately, pulling that ID started taking 2–3 minutes. Sales and marketing teams were often on the phone with customers, waiting for the number before they could continue. It was a terrible experience. ...

How to run the agent (generic Java) and where the metadata is used

GraalVM Native Image Agent - reachability metadata: how to run it, where files go

In short Run the app java -agentlib:native-image-agent=config-output-dir=./graalcnf/ -jar target/app.jar Copy the generated files from ./graalcnf/ to the project under src/main/resources/META-INF/native-image/<groupId>/<artifactId>/ Build the native image mvn -ntp package -Pnative -DskipTests TLDR Native Image needs reachability metadata so it can include dynamic features your app uses at run time (reflection, resources, proxies, serialization, JNI). The simplest way to get this metadata is to run your app on the JVM with the Native Image Agent and then use the generated JSON files during the native build. ...

How to use Testcontainers with PostgreSQL and SSL

This guide walks you through running PostgreSQL in Testcontainers with SSL enabled and client-certificate authentication (verify-full). It explains: How to generate a CA, server, and client certificates. How to prepare certificate/key files and the right formats/permissions. How to configure PostgreSQL (postgresql.conf and pg_hba.conf) to require client certificates. How to wire everything up in Testcontainers. How to connect from Java (JDBC) and optionally from the psql CLI. Everything here is based on the code in this repository, particularly: ...