Onno Vos

Onno Vos

Senior Engineer at Klarna performing open heart surgery on its main Erlang system

Onno was pulled into Erlang about 5 years ago, while working at Klarna. A match made in heaven started and his love for Erlang is stronger than ever. At Klarna he has worked on various parts of the main Erlang system and after coming back to Klarna, for the past 1,5 years his love of Postgres was merged with his love for Erlang as the team is working hard on moving the old system to an even more scalable system!

Past Activities

Dániel Szoboszlay / Onno Vos
Code BEAM V Europe
20 May 2021
13.10 - 13.50

Breaking up with Mnesia

Klarna runs its business on Mnesia from day one. 16 years later we're still together... but we’re heading towards a break up.
How did we get here? What’s the way forward? Over the years problems hit us for sure, but as we’re about to part we also found good in Mnesia we'd taken for granted and never appreciated before. Are you just launching on Mnesia? Come and learn how not to corner yourself by the time you grow to a Unicorn. Already stretching limits? See how we made Postgres a viable replacement.


Mnesia has some superpowers, but you won’t realise they exist until you try to live without them. Become aware of them, and you will be able to make conscious choices on whether to fully utilize them or to keep your options open.


Developers using Mnesia - or even Postgres, if they’re interested in our journey towards performant serializable transactions on this database.