System Design · advanced
Collaboration Systems
OT, CRDT, conflict resolution.
Mental model
Collaborative editors pick one of two conflict-resolution models: Operational Transform (OT), which mathematically rewrites concurrent edits, or CRDTs, which use data structures that merge automatically. CRDTs handle offline well; OT is more compact on the wire. Pick by your latency and offline needs.
How to study Collaboration Systems
Begin by restating the mental model in your own words, then connect it to a concrete system you have built or operated. Name the mechanism, the constraint it addresses, and the trade-off it introduces. Use System Design Primer, A Conflict-Free Replicated JSON Datatype (Kleppmann & Beresford), Local-first software: you own your data, in spite of the cloud to check details, but close the source before writing your explanation. Retrieval is the learning step; rereading is only preparation.
Next, compare Collaboration Systems with the neighboring concepts in its roadmap. Ask what changes in correctness, latency, resource use, operability, and failure recovery. Complete Collaborative doc editor and preserve the command, input, output, and one failed attempt as evidence. Finish by explaining the idea without jargon to someone who has not studied the track.
Proof of understanding
- Explain the mechanism from first principles and identify the state it reads or changes.
- Give one situation where the concept is the right choice and one where it is not.
- Predict a realistic failure mode before running the drill, then compare the prediction with evidence.
- Connect the result to a roadmap or build artifact instead of treating the concept as isolated trivia.
Learn from primary sources
Practice and explain it back
Collaborative doc editor
Design a Google-Docs-style collaborative editor for 2-50 concurrent editors. Pick a conflict resolution model (OT vs CRDT) and explain the sync protocol.
Expected evidence: Conflict model + a worked example of two concurrent edits being merged.
Open the interactive drill →Review prompts
- What must be true of the server for OT to be correct, and why do CRDTs not need it?
Build evidence
Use a roadmap capstone to turn this concept into working evidence.
Related concepts
None assigned yet.