Matthew Weidner

Fun academic find: the core idea of server reconciliation (a general approach to real-time collaboration that's simpler than Operational Transformation or CRDTs) already appears in an MIT tech report from 1985.

I learned of this from the first paper on collaborative text editing (dl.acm.org/doi/abs/10.1...), which cites the idea but claims it won't work for text. Instead they introduce Operational Transformation, which led to a lot of academic work but is more complicated.

Fun academic find: the core idea of server reconciliation (a general approach to real-time collaboration that's simpler than Operational Transformation or CRDTs) already appears in an MIT tech report from 1985.

From the ~1st collaborative text editing paper: if two users do "delete char @ index 7" concurrently, no serial ordering gives the correct answer. So the authors abandon serializability, leading to OT/CRDTs. But if you rephrase the ops as "delete char @ <per-char id>", both serial orders work!

For many collaborative apps, though, you can get away with just serializing all users' ops. E.g., apply ops in the order a server receives them. This strategy appears in Replicache and in @tanstack.com DB (taking over from ElectricSQL v0's fancier CRDT-based strategy).

From the ~1st collaborative text editing paper: if two users do "delete char @ index 7" concurrently, no serial ordering gives the correct answer. So the authors abandon serializability, leading to OT/CRDTs. But if you rephrase the ops as "delete char @ <per-char id>", both serial orders work!

(The paper is "Concurrency control in groupware systems", Ellis & Gibbs 1989. doi.org/10.1145/6754...)

New blog post: "Collaborative Text Editing without CRDTs or OT". It describes what I hope is a simpler and more flexible approach to the hardest part of a collaborative app, text editing. mattweidner.com/2025/05/21/t...

I'll be talking about this approach at Local First Conf next week.