Comment by pas

yes and no, as the sibling comment mentions sometimes a message bus is used (Kafka, for example), but Netflix is (was?) all-in with HTTP (low-latency gRPC, HTTP/3, wrapped in nice type-safe SDK packages)

but ideally you don't break the glass and reach for a microservices architecture if you don't need the scalability afforded by very deep decoupling

which means ideally you have separate databases (and DB schema and even likely different kind of data store), and through the magic of having minimally overlapping "bounded contexts" you don't need a lot of data to be sent over (the client SDK will pick what it needs for example)

... of course serving a content recommendation request (which results in a cascade of requests that go to various microservices, eg. profile, rights management data, CDN availability, and metadata for the results, image URLs, etc) for a Netflix user doesn't need durability, so no Kafka (or other message bus), but when the user changes their profile it might be something that gets "broadcasted"

(and durable "replayable" queues help, because then services can be put to read-only mode to serve traffic, while new instances are starting up, and they will catch up. and of course it's useful for debugging too, at least compared to HTTP logs, which usually don't have the body/payload logged.)