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Code RoomSIP session routing layer
HardPrep Room Coding #3768

SIP session routing layer

System designNetworking & APIsReliability & on-callSenior–Staff~50 min

Design a carrier-grade SIP session routing layer (a stateful SIP proxy / SBC tier) that handles 100k concurrent calls and 5k call setups/sec, routing SIP signaling to the right media gateway / downstream carrier based on dialed number, originating trunk, and least-cost routing rules. Requirements: call-setup p99 under 150ms, five-nines availability, no dropped active calls when a proxy node fails over, and routing-table/LCR updates that converge without misrouting calls mid-flight. Walk through the signaling architecture, the routing/failover model, and the central trade-off.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.

Clarify5:30 left
Estimate5:30 planned
Design16:30 planned
Deep dive13:30 planned
Failure9:00 planned
0:00
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.