When a failed payment means license risk, you need systems that handle peak traffic without breaking.
For the curious: there is a tiny machine hiding in the banner.
Billions of messages/day IoT system
Stabilized core payment system
Acquired in 18 months
Typed Erlang language features
"Tobias is one of the more talented Engineers I have had the pleasure to work with... I can highly recommend Tobias and there will always be an open position in my organization for him."
"His background having lead and scaled technical teams at Klarna was a distinguishing factor... I would highly recommend Happi to any early stage founders and executives building in tech."
"Eventually, and also thanks to Erik's contribution, our company was acquired by a strategic buyer after only 18 months mainly due to our innovative technology."
"If you are searching for a motivated team that will go the last mile with you, deliver qualitative stuff and understand bad jokes…Happihacking is the right choice!"
Your System, Built to Last
Your fintech backend needs to handle millions of transactions without failing. When payment systems break, you face regulatory fines and lost customer trust.
You can't afford downtime. Your architecture determines whether you scale smoothly or face costly failures at peak traffic.
How You Get Reliable Scale
Your payment system needs proven architecture that handles peak traffic without errors. Companies like Meta and Klarna trust BEAM-powered backends for billions of daily transactions.
You start with a system audit to find failure points, then architect solutions that prevent outages before they happen.
Result: Your system scales smoothly under peak load. Your compliance team stays confident. Your customers experience zero payment failures.
See how you get there →Proof, Not Promises
The strongest argument for this work is the track record. These case studies show the kind of systems, stakes, and outcomes HappiHacking has already handled.
Klarna
Scaled engineering from 1 to 80
Erik led Klarna’s early technology organization and core payment platform through hypergrowth.
Deutsche Telekom
Billions of IoT messages per day
Architecture and proof-of-concept delivery for high-volume data ingestion and analysis.
Travel SaaS
Acquired in 18 months
Interim CTO work spanning architecture, hiring, and execution during a critical MVP phase.
Sika Health
Founder-level technical advising
Early roadmap, team planning, and executive guidance for a healthcare payments company.
Your Questions Answered
My system is very complex, can you help?
Schedule a call to discuss your specific challenges and how you can prevent costly failures.
What if your plan seems too risky for my business?
You start with a two-week proof of concept. You can see results before committing to the full architecture sprint.
How do you ensure your solution works under load?
Every solution includes load testing and failure simulation so you know your system won't break at peak traffic.
Can you provide a fixed price?
Yes. Your Scale Audit (€15k) and Architecture Sprint (€45k) have fixed scopes and guaranteed deliverables.
Ready to Scale Your Fintech Backend?
Let's discuss how we can help your compliance team sleep at night.
Prefer a Lower-Commitment Starting Point?
Training is available separately for teams who want to sharpen their architecture and runtime understanding before bringing in consulting. It is grounded in the same production lessons that shape the client work.
The BEAM for Developers runs next as a public ElixirConf EU training in Malaga on April 22, 2026. Private workshops are also available.
Work Directly With the People Selling the Work
Erik Stenman is the principal consultant and the core technical selling point: former Klarna CTO, PhD in Computer Science, BEAM expert, and the person prospects actually want to evaluate before a serious engagement.
Anna Attefall leads consulting delivery and makes sure strategy turns into a project that moves cleanly.
See Erik and Anna