Definitions
Bad-call rate — share of calls with a quality problem (audio / video / connection).
P2P vs Meet — P2P = 1-to-1 call; Meet = group call.
Not-ring — the callee did not get a proper ring (call-setup stage).
• delay-ring — rang but late (push / signaling latency).
• silence / never-ring — never rang at all.
OTP — one-time verification-code SMS.
Auto-fill — code auto-entered on Android (SMS Retriever).
Routing optimization — send each country OTP via its cheapest qualified vendor.
eBPF — kernel-level network optimization → less CPU per node → fewer machines.
pp — percentage points.