We never had a good experience with trying to utilize a database in any of our project, disregarding if it's NoSQL or SQL.
Particle devices has this utility called WebHooks, where we can make HTTP request to a specified host, where Holochain application can get hosted with domain name of user's choice and be utilized by user with incoming POST requests. For example, holoapp.com/fn/zomename/someFunction will invoke the execution of the codebse in someFunction() of Holochain application, and be stored inside it's distributed hash table.
Lack of hardware to increase the convenience.
Use this proof of concepts to further promote Holochain.