Software engineer & consultant · Oslo, NO

Kristoffer
Opsahl

Backend-leaning full-stack, with security and the low-level details part of how I work. I build with Java, Spring Boot & React, Apache Kafka for event-driven systems, and Elixir & Phoenix when concurrency calls.

Distributed Systems
Event-Driven Architecture
Application Security
Cryptography

Forgejo ActionsSQL ServerOAuth 2.0RustWebAuthnReactKeycloakKubernetesPasskeysKotlinAzureGitHub ActionsSAML 2.0MySQLCaddyiOSJavaDebianAndroidElixirDockerGCPTypeScriptPhoenixApache KafkaLinuxPostgreSQLSpring BootReact NativeExpoBashGoGitLab CI/CDFIDO2OpenID ConnectJWTSQL

Latest

all →

2026-04-03

How to Securely Erase a Hard-Disk Drive

LinuxNote

2025-12-07

Coding Agents Need Deterministic Feedback: A Case for Phoenix

AIElixir

2025-09-14

Using dd to Write an .iso to a USB Drive

LinuxNote

2025-07-07

My Alacritty, Zellij, and Helix Development Setup

ToolingNote

2025-04-29

Breaking AES-ECB with an Encryption Oracle Attack

SecurityCryptography

2025-04-22

3rd Prize at TG:HACK

SecurityCTF

2025-03-25

Java's Optional Has a Problem

Java

2025-03-07

From Zero to Hello World with Apache Kafka® in 2025

KafkaTutorial

2025-03-06

Core Concepts in Apache Kafka®

Kafka