replication

Split-brain writes are a fencing failure first and a data problem second. Freeze writes, read the divergence boundary from replication positions, and let the payment ledger arbitrate reality.

Stateful firewalls keep established flows alive after their rule vanishes, so cleanup day passes every check and lag appears days later. Flow logs name the hour; inventories prevent the repeat.

The classic napkin-math question. The number in the prompt is the question, and candidates who draw the architecture before doing the arithmetic design something the physics forbids.

The design round where the honest answer is mostly about data. Stateless traffic across regions is straightforward; the database is where active-active is either solved or pretended.

Every candidate says replication and failover. The scoring answer names the replication mode, states the resulting data loss window, and explains how the cluster avoids two primaries.

Size stored sessions from expiry and creation rates, then decide how quickly logout must take effect and what failover may forget.