Good point. One thing that’s important to distinguish is whether they are purposely keeping HA out of the open source product as a business strategy (as many “open source” database/search vendors do these days), or they just haven’t developed it. From what I can tell, it’s the latter - they fully intend to support this feature in the open source project and would welcome contributions to do that, but it has been repeatedly delayed / de-prioritized. (The PR that Dave linked to is from a Meilisearch employee.)
So I am optimistic that this could be resolved in the future, but it seems like nobody should count on that anytime soon.
It’s also worth noting that (if I understand correctly) the nominal “high availability” that they advertise on their cloud offering is not replication-based but instead “we ensure the high availability of your project with Kubernetes technology, redundant volumes, and regular backups. In the event of an error, a Meilisearch server takes only a few milliseconds to restart” (source). So Open edX operators may not be able to use replication in the immediate future, but can certainly use those strategies. What’s more, because Meilisearch is so lightweight, you can deploy a separate instance per index, so that (for example) your Studio courseware search doesn’t go down at the same time as your forum search.
Q: Would this be a deal-breaker?
Q: Is ElasticSearch ever on the “critical path” for learning? i.e. learner account creation, logging in, course purchasing/enrollment, viewing courseware, submitting assignments/exams/problems, posting in the forum, viewing grades, etc.