The server crashed mid-push. Priya still got her alert.

transcript

Arjun pays Priya. The server holding her live connection dies, mid-push. She still sees the alert. Nothing lost. So how?

Why not push it straight down the socket? It's fast. But one crash, one Wi-Fi drop, one deploy, and it's gone. Nowhere else. So flip the order. Write it down first, with a number. Then send a hint.

Arjun pays Priya 2,400 rupees. Her web app is open. First, it goes into her durable inbox. Sequence number 1184. Then a tiny hint goes to gateway 17. Sequence 1184 is ready. And gateway 17 crashes. Right before the socket write.

Her browser notices, and reconnects to another gateway. It asks one question. Everything after 1183, please? 1184 comes back from the inbox. 2,400 rupees received, from Arjun.

Lose the hint, and the client just resumes from the inbox. The socket is the fast path. The inbox is the record.

Full breakdown in the lecture.