Start a rest server by running:
bin/rest 8888 myalias "datomic:mem://"
Then interact with it with curl:
curl -i -X PUT http://localhost:8888/db/myalias/seattle # Create a database
curl -H Content-Type: -H "Content-Type:" -X POST -d @- http://localhost:8888/db/myalias/seattle
[
{:db/id #db/id[:db.part/db]