[nolanl]

(I also work on PouchDB.)

For "conflict-free sync," according to the docs, this appears to be last-write-wins along with a special case for deletes: https://realm.io/docs/realm-object-server/#conflict-resoluti... . (Incidentally Couch/Pouch also has a special case for deletes, but it does the opposite behavior by default – deletions lose to updates.)

There's also some language in here about how "insertions in lists are ordered by time;" I'd be curious to know how they coordinate clock times across nodes. Ditto for "last update wins" – important to know how "last" is determined.

In general, I tend to be skeptical of systems that hinge on last-write-wins, but LWW is definitely a model that works in a lot of cases where you're not too concerned about the possibility of losing data, and it's also a simpler mental model for the app developer.

[astigsen]

Realms approach to conflict resolution is very different from what you see in products like Couch. Realm is an _object_ database, so in contrast to document databases where conflict resolution happens very coarse grained at the document level, in Realm it happens at the object level (and actually all the way down into individual properties).

This essentially means that the entire object graph is treated as one big CRDT [0], transparently handling conflict across individual objects, properties and relations.

When talking about ordering by time, both in the context of LWW and insertions in lists, we are talking about vector clock time, not necessarily device time (or though that is taken into account as well).

[0] https://en.wikipedia.org/wiki/Conflict-free_replicated_data_...

[gritzko]

An-object-graph-as-a-CRDT is a really interesting concept. So far, I am not aware of any literature formalizing/studying it. I can only recall the recent CRDT JSON paper by Kleppmann et al, which is significantly less ambitious. Is your approach documented?

While reading the announce, my first guess was some recursive per-field LWW, but you mentioned vector clocks. That is intriguing.

[pfraze]

LWW is a tradeoff. You'll be better off selling it as an automated-resolution option on top of manual resolution, instead of an innovation over manual resolution. (MV registers are a CRDT as well!)