OpenTelemetry vs Datadog APM vs New Relic

A team picking an observability stack today almost always hits this fork: standardize on OpenTelemetry, or buy into a full platform like Datadog or New Relic. Interviewers use this question to see if you understand the tradeoff, not just the product names.

The answer interviewers want

OpenTelemetry is the open standard for telemetry collection. It's free and vendor-neutral, meaning the instrumentation you write - traces, metrics, logs - isn't tied to any single backend. You can swap where that data goes without re-instrumenting your services.

Datadog and New Relic are full-stack observability platforms. They give you advanced analytics, dashboards, anomaly detection, and a polished UI out of the box, but they cost more and the deeper you integrate, the harder it is to leave.

The smart pattern most mature teams land on: use OpenTelemetry to instrument and collect telemetry, then decide on a backend later. You can send that data to Datadog, New Relic, an open-source stack, or anything that speaks OTLP. The instrumentation layer stays yours. The backend becomes a swappable component instead of a foundational commitment.

The key point to make explicit in an interview: avoid the vendor trap from day one. If you instrument directly against a proprietary SDK, switching vendors later means rewriting instrumentation across every service. If you instrument with OpenTelemetry first, switching vendors is a configuration change in your collector, not a migration project.

Why interviewers ask this

This question is a proxy for architectural judgment, not product trivia. Interviewers want to know if you think about observability as a long-term platform decision or just whichever tool the team happened to buy first. They're also probing whether you understand the cost/control tradeoff: platforms like Datadog and New Relic save engineering time and add analytics power, but at the price of lock-in and spend. A candidate who can articulate both sides, and who defaults to decoupling collection from backend, signals they've actually run observability at scale rather than just read about it.

Follow-ups to expect

Why not just use Datadog's native agent and skip OpenTelemetry? You can, and it's often faster to get started, but every bit of instrumentation becomes Datadog-specific, so a future vendor switch or cost renegotiation gets expensive fast.

Does using OpenTelemetry mean you don't need Datadog or New Relic at all? No. OpenTelemetry is the collection layer; you still need a backend to store, query, and visualize the data, and that backend can absolutely be Datadog or New Relic.

What's the actual cost tradeoff here? Full platforms cost more in licensing but less in engineering time for analytics and dashboards; OpenTelemetry costs more upfront in setup but preserves flexibility and avoids lock-in later.

The common wrong answer

Most candidates treat this as a feature bake-off, listing dashboard quality or pricing tiers, and never mention lock-in at all. That answer sounds like someone who evaluated tools from a vendor's sales deck, not someone who had to migrate an observability stack under pressure.