Zelvarion
Long-form technical notes, written by operators for operators.
Structuring DNS for Reliability
August 18, 2026
Domain resolution outages produce an awkward paradox: server instances remain perfectly healthy while clients perceive complete downtime. Insulating against platform-level registrar outages demands secondary authoritative DNS providers operating over separate routing infrastructure.
Configuring record expiration windows involves competing operational goals. Low TTL values promise rapid agility but multiply resolver query rates and propagate minor transit anomalies; high values cushion against upstream downtime while locking migrations in place. A tiered configuration assigning low TTLs to failover routes and long durations to invariant records performs best.
The Hidden Cost of Chatty Microservices
April 14, 2026
Refactoring centralized code into independent microservices trades code complexity for network unpredictability. Workflows that previously triggered simple internal methods suddenly require coordinated remote requests, each introducing separate latency budgets, retry loops, and partition hazards.…
A Practical Guide to API Rate Limiting
September 4, 2026
Few infrastructure components are treated with as much casual oversight as traffic throttling. Simple IP-based token buckets fall apart the moment traffic traverses cellular NAT gateways, causing thousands of legitimate handsets to suffer collective penalties for a single neighbor's surge.…
Why Edge Caching Still Matters in 2026
April 18, 2026
Periodic declarations that edge caching is dead consistently overlook networking realities: fiber lines still obey physical constraints. Even with cheap bandwidth and fast runtimes, a round trip between Sao Paulo and Frankfurt easily consumes hundreds of milliseconds. No amount of runtime tuning can…
Email Deliverability: Authentication Beyond SPF
June 27, 2026
Traditional SPF checking fails to address modern deliverability challenges on its own. While an envelope IP check might succeed, mismatched headers trigger spam filters that prioritize cryptographic DKIM validations and broader DMARC policy rules.…
More reading
- Managing Secrets Without Losing Sleep — Security, May 11, 2026
- Cache Invalidation Patterns That Survive Traffic — Data, May 6, 2026
- Understanding TLS 1.3 Session Resumption — Security, June 19, 2026
About us
Our contributors have spent years on-call for large platforms. This site collects the playbooks, postmortems and reference material we wish someone had handed us earlier.