This does require that your backend datamodel is key/value oriented like Replicache, so that the same code can run against both storage systems with minimal branching.
Although using a relational database as a document store is somewhat unconventional, Postgres has excellent JSON support and does support this usage. This can be a very convenient way to get a Replicache project up and running quickly.
replicache-transaction Helper Package
We provide the
replicache-transaction package to make this usage easier. It adapts Replicache's
WriteTransaction interface to some backend key/value storage that you provide. See
replicache-express for an example.
Other Backend Datastores
If you want to use Replicache with some non-key/value backend datastore, such as a normalized SQL database, it typically makes more sense to implement the mutators twice.
See Replicache on Rails for a JS helper library that can automate much of the client-side.