JWJuha Wilppuinblog.juhawilppu.com·Dec 17, 2025 · 3 min readMy side project: 8 years in production, €13M invoicedIn early 2017, I launched a side project called Siikli. It’s a simple, mission-critical ERP that has been used to invoice over €13M. (To clarify: That figure is the amount invoiced by my users, not my revenue.) How it started In 2016, a friend asked ...00
JWJuha Wilppuinblog.juhawilppu.com·Dec 11, 2025 · 3 min readZero-downtime region migration (from US to Europe)Recently, I migrated our production servers from the US to Europe with zero downtime. The technical execution was straightforward with our plan, but caused one issue. Why we migrated We originally launched our servers in the US with high expectations...00
JWJuha Wilppuinblog.juhawilppu.com·Oct 29, 2025 · 3 min readMultiplayer math game I built in 2013Back in 2013, I tried to reinvent how kids learn math by building a competitive online multiplayer game. I tested it in a real classroom with 20 students. Here’s how it went. The idea I believed that competition would motivate students. Kids who norm...00
JWJuha Wilppuinblog.juhawilppu.com·Oct 26, 2025 · 2 min readIP whitelisting mitigated a critical security issueIP whitelisting is old-school. But it’s also a simple way to add a surprisingly strong second layer of defence. Here’s how it saved us during a security audit. The mistake: Trusting the Host header We had a vulnerability in the “Forgot password” feat...00
JWJuha Wilppuinblog.juhawilppu.com·Aug 5, 2025 · 2 min readBest-in-class backups in AWSMany years ago, I lost production data that I couldn’t recover. I remember looking at the screen in disbelief. The mix of regret and helplessness is something I never want to experience again. Today, I use a “paranoid” backup strategy built on immuta...00