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Interview Guide Jul 19, 2026 14 min read

Designing for Observability: Distributed Tracing, Metrics & OpenTelemetry

You cannot manage what you cannot measure. How to incorporate distributed tracing, Prometheus metrics, and OpenTelemetry context propagation into high-level designs.

Interview GuideObservabilityOpenTelemetryMetricsArchitecture
HFHLDForge Architecture TeamStaff Observability Architect

1. The Three Pillars of Observability

Distributed Tracing: Visualizing request flow across 20 microservices with unique Trace IDs and Span IDs. OpenTelemetry (OTel) provides vendor-neutral instrumentation.

Metrics: High-cardinality time-series data (Prometheus / Datadog) tracking throughput, error rates, and CPU utilization.

Structured Logs: JSON formatted log streams aggregated in Elasticsearch / ClickHouse with correlated Trace IDs.

2. The RED and USE Metrics Frameworks

RED Method (for Request-Driven Services): Rate (requests per second), Errors (failed requests), Duration (latency distribution).

USE Method (for Resources: CPU, Memory, Disk): Utilization (time resource was busy), Saturation (queued work waiting for resource), Errors (error count).

3. SLI, SLO and Error Budgets

Define realistic Service Level Indicators (SLIs) and Service Level Objectives (SLOs). For example: '99.9% of payment authorizations complete in <500ms over a 30-day window.' The remaining 0.1% is the team's Error Budget for shipping features quickly.

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Written by HLDForge Architecture Team

Staff Observability Architect

The HLDForge Architecture Team publishes practical engineering guides, real-world case studies, and high-concurrency blueprints to help engineers build scalable and fault-tolerant software.

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