Challenge 1: Pick the Right Streaming Mode — Possible Solution
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(a) A client uploading a large log file in 1MB chunks, getting one
confirmation back — CLIENT STREAMING.

rpc UploadLogFile(stream LogChunk) returns (UploadConfirmation);

The client sends MANY messages (each 1MB chunk) over time, and only
ONE response comes back once the upload completes — exactly the
many-requests-one-response shape client streaming is built for,
matching this chapter's own UploadReadings example.

(b) A dashboard subscribing to live order-count updates — SERVER
STREAMING.

rpc WatchOrderCount(WatchOrderCountRequest) returns (stream OrderCountUpdate);

The dashboard sends ONE request to establish the subscription, and the
server pushes MANY responses over time as new counts become available
— exactly the one-request-many-responses shape server streaming is
built for, matching this chapter's own WatchPrice example.