OpenTelemetry
OTLP, Context Propagation & Backends
Connect the dots: how OTLP and context carry data across services to any backend.
Two mechanisms make OpenTelemetry work end to end. OTLP (the OpenTelemetry Protocol) is the standard wire format — gRPC or HTTP — for shipping traces, metrics, and logs between SDKs, Collectors, and backends. Because nearly every vendor accepts OTLP, it is the lingua franca that lets you point instrumentation at a new backend by changing an endpoint, not your code.
A shipping system where every parcel uses the same barcode standard (OTLP) and carries a tracking number passed hand to hand (context propagation), so any depot (backend) can reconstruct the parcel's entire journey.
Key Concepts
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Context propagation is what links spans across service boundaries into one trace. When service A calls service B, the SDK injects the current trace context into the request (the W3C traceparent header is the standard), and B extracts it so its spans share the same trace ID and nest under the caller. Baggage propagates arbitrary key/value context (like a tenant or request priority) the same way. The backend — Tempo, Jaeger, a vendor, or a database — then stores and reconstructs the full trace. The framing for interviews: OTel produces and propagates; OTLP transports; the backend stores and visualizes.
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What the interviewer is probing.
What the interviewer is probing.
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1. "What is OTLP?" *Probing:* the vocabulary. *Stalls:* "A format." *Moves up:* the
OpenTelemetry protocol — the wire format over gRPC or HTTP that most backends now accept natively.
1. "What is OTLP?"
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2. "How does context propagate?" *Probing:* the mechanism. *Stalls:* "Automatically." *Moves
up:* W3C traceparent and tracestate headers, with baggage for carrying application values alongside.
2. "How does context propagate?"
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3. "What breaks propagation in practice?" *Probing:* experience. *Stalls:* "Nothing." *Moves
up:* asynchronous boundaries — thread pools, message queues and batch jobs — where the context must
be carried explicitly.
3. "What breaks propagation in practice?"
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4. "What is the real benefit of standardising on OTLP?" *Probing:* the commercial angle.
*Stalls:* "Tidiness." *Moves up:* backends become a configuration change rather than a migration
project, which is genuine negotiating leverage at renewal.
4. "What is the real benefit of standardising on OTLP?"