Network & Infrastructure / DNS, DNSSEC & Service Discovery
Recursive DNS capacity under cold-cache failure conditions
A resolver cluster handles normal load comfortably but saturates after restart or upstream degradation. Warm-cache query rates can substantially understate the work required during a failure.
Environment and inputs: Authoritative and recursive DNS infrastructure; BIND examples are conceptual and require release-matched configuration. Diagnostic/design example; not tested on production equipment.
Collect the evidence
Measure cache hit ratio, outstanding recursion, upstream response time, retries and client request volume. Separate unique-name workloads from repeated popular-name lookups.
Explain the result
Recursive capacity depends on upstream work and concurrency, not just received queries per second. Slow or failing authorities can hold resources while retries increase demand.
Plan the fix
Capacity-plan cold-cache and partial-upstream-failure scenarios with bounded recursion and appropriate client distribution. Avoid making all instances cold simultaneously during routine maintenance.
Check the result and rollback
Load-test realistic name distributions and degraded authorities in isolation. Restore previous rollout settings if cold starts exceed the response budget or one failing namespace consumes disproportionate recursive capacity.