Author here- and yes as a disclaimer I work at Convex.
As a caveat to that disclaimer, I pivoted my career to work here b/c I genuinely believe it moves the industry forward b/c of the default correctness guarantees, along with other things.
To this question here, some of the things that accelerate full stack development:
1. Automatically updates your UI when DB data changes, not just on a per-document one-off subscription, but based on a whole server function's execution which is deterministic and cached. And regardless if the changes were made in the current browser tab or by a different user elsewhere. Not having to remember all the places to force refresh when a user updates their profile name, e.g., makes it way faster. And not only do the Convex client react hooks fire on data changes, the data they return for a page render is all from the same logical timestamp. You don't have to worry about one part of the UI saying that payment is pending when another says it's been paid.
2. End-to-end types without codegen. When you define a server function, you define the argument validators, which immediately show up on the types for calling it from the frontend. You can iterate on your backend function and frontend types side-by-side without redefining types or codegen in the loop.
3. Automatic retries for database conflicts, as well as retries for mutations fired from the client. B/c mutations are deterministic and side-effect-free (other than transactional changes to the DB and scheduler), the client can keep retrying them and guarantee exactly-once execution. And if your mutation had DB conflicts, it's automatically retried (up to a limit with backoff). So the client can submit operations without worrying about how to recover on conflict.
There's obv. a bunch more in the article about features like text search and other things out of the box, but those maybe are more conveniences on the backend, since maybe a frontend person wouldn't have been setting up Algolia, etc.
