Courses/Mobile System Design/Lab
Handbook
Case 01 · Real-time chat

Design 1:1 and group messaging. Messages should arrive in under a second, show sent, delivered and read, and users must be able to keep typing on a flaky connection.

p95 delivery < 1 sworks offlinereceiptsTap to place: tap a block in the library to drop it on the canvas, tap the blue dot on a block, then tap the block it should connect to. Everything else works the same as on a laptop.Watch the walkthrough for this case →
on the phonethe internet
drag blocks around · click the blue dot, then another block, to draw an arrow