RelayPlane vs Datadog LLM Observability
Datadog LLM Observability is an add-on to Datadog's enterprise monitoring platform that requires the Datadog agent and dd-trace SDK instrumentation. RelayPlane is an MIT-licensed npm package that runs on localhost with no agent, no code changes, and no existing infrastructure required.
TL;DR
Choose RelayPlane when you want:
- npm install and running in 30 seconds, no agent required
- No code instrumentation, just an OPENAI_BASE_URL env var
- Local SQLite cost tracking with no data leaving your machine
- Works without an existing Datadog subscription
- Claude Code and Cursor integration out of the box
Datadog LLM Observability may work for you if you need:
- LLM traces correlated with existing Datadog APM, infrastructure, and alerts
- You are already a Datadog customer and want unified dashboards
- Enterprise compliance and SLA requirements already met by Datadog
- Team already uses dd-trace for existing APM instrumentation
Feature Comparison
| Feature | RelayPlane | Datadog LLM Observability |
|---|---|---|
| Product type RelayPlane is a standalone npm package you run on localhost. Datadog LLM Observability is not a standalone product: it is a feature layer on top of Datadog's existing infrastructure monitoring platform, requiring an active Datadog subscription and agent deployment. | npm-native LLM proxy (local-first) | LLM observability add-on to Datadog's broader APM and monitoring platform |
| Install method RelayPlane ships as an npm package: one command and you are proxying LLM requests locally. Datadog LLM Observability requires installing the Datadog agent on your host, instrumenting your code with the dd-trace SDK, and configuring a DD_API_KEY. There is no npm package for standalone LLM proxy use. | npm install -g @relayplane/proxy | Datadog agent + dd-trace SDK + DD_API_KEY environment variable |
| No account required RelayPlane starts with no signup, no credit card, and no cloud dependency. Datadog requires a Datadog account, an active plan, and a DD_API_KEY before any LLM traces can be captured. Trial accounts are available but the platform is not operable without credentials. | ||
| No code instrumentation required RelayPlane requires only an OPENAI_BASE_URL environment variable change, with no code modifications. Datadog LLM Observability requires wrapping your LLM calls with the dd-trace SDK's LLMObs module, adding explicit trace spans and metadata to your application code. | ||
| Standalone (no existing platform required) RelayPlane works as a standalone tool with zero infrastructure dependencies. Datadog LLM Observability is only useful if you already run Datadog for infrastructure monitoring. For teams not already on Datadog, adopting it purely for LLM observability means committing to Datadog's full platform and pricing. | ||
| Pricing model RelayPlane has no paid gateway tier. Datadog pricing is per-host for infrastructure monitoring plus usage-based charges for APM spans and LLM observability data. LLM Observability is an add-on cost on top of existing Datadog subscription spend. Pricing is negotiated for enterprise contracts. | MIT open source, free to self-host | Add-on to existing Datadog plan; enterprise pricing; per-host and usage-based |
| Self-hosted / local-first RelayPlane runs entirely on localhost and stores logs in a local SQLite file. Datadog is a cloud-only SaaS platform with no self-hosted deployment option. All trace data is sent to Datadog's cloud infrastructure. | ||
| No data leaves your machine RelayPlane stores all request logs locally by default. Datadog LLM Observability sends all traces, prompts, completions, and metadata to Datadog's cloud. For teams with data residency requirements or sensitive prompt content, this is a significant distinction. | ||
| Language support RelayPlane is a transparent HTTP proxy: any language or tool that supports OPENAI_BASE_URL works automatically. Datadog LLM Observability provides instrumentation via dd-trace for Python and Node.js. Other languages require manual span creation. | Any language via OPENAI_BASE_URL (transparent proxy) | Python and Node.js (dd-trace SDK wrappers) |
| npm package for LLM proxy RelayPlane publishes @relayplane/proxy to npm for easy global installation. Datadog has no npm package for standalone LLM proxying. dd-trace is available on npm but requires full SDK instrumentation and a Datadog account to function. | ||
| Works with Claude Code and Cursor RelayPlane is designed for Claude Code, Cursor, Windsurf, and Aider with direct integration docs, via a single OPENAI_BASE_URL swap. Datadog LLM Observability requires SDK-level code instrumentation and is not applicable to AI coding assistants that call LLM APIs directly. | Not supported (requires code instrumentation, not compatible with editor tools) | |
| Local cost tracking RelayPlane logs every request's exact dollar cost in local SQLite with no data leaving your machine. Datadog can surface LLM cost metrics through its dashboard, but this requires the full platform setup and all data is stored in their cloud. | Via Datadog cost dashboards (cloud only, requires full platform setup) | |
| APM and infrastructure correlation Datadog's strength is correlating LLM traces with broader application performance data, infrastructure metrics, logs, and alerts across your existing Datadog dashboards. RelayPlane focuses on local cost tracking and intelligent model routing without APM integration. | ||
| Existing Datadog infrastructure integration If your team already runs Datadog for infrastructure monitoring, LLM traces can appear alongside existing dashboards, alerts, and SLOs without a new vendor. RelayPlane is a standalone tool that does not integrate with Datadog. | ||
| Complexity-based model routing RelayPlane routes simple tasks to cheaper models based on request complexity, reducing costs automatically. Datadog LLM Observability is an observability tool, not a routing proxy: it does not intercept or route LLM requests. | ||
| Open source RelayPlane is MIT licensed. Datadog is a proprietary closed-source SaaS platform. There is no open-source or community edition of Datadog LLM Observability. | MIT |
Why Developers Choose RelayPlane Over Datadog LLM Observability
One npm command vs Datadog agent + SDK instrumentation + DD_API_KEY
npm install -g @relayplane/proxy and you are proxying LLM requests in under 30 seconds. Datadog LLM Observability requires installing the Datadog agent on your host, adding dd-trace to your application, wrapping your LLM calls with LLMObs.wrap() or similar SDK calls, and configuring a DD_API_KEY environment variable. For a developer who just wants to see what their LLM calls cost, that is a multi-hour setup against an enterprise monitoring platform, not a five-minute install.
No existing Datadog subscription required
Datadog LLM Observability is an add-on to Datadog's existing monitoring platform. If you are not already a Datadog customer, adopting it purely for LLM observability means onboarding to Datadog's full pricing model: per-host infrastructure fees, APM span costs, and enterprise contract negotiation. RelayPlane is MIT open source with no subscription required, no per-host pricing, and no vendor relationship to manage.
Your prompts and completions stay on your machine
RelayPlane stores all request logs, including prompt content and model completions, in a local SQLite file on your machine. No data leaves your environment by default. Datadog LLM Observability sends all trace data, including prompt and completion content, to Datadog's cloud infrastructure. For teams working with sensitive prompts, proprietary context, or regulated data, that distinction matters regardless of Datadog's compliance certifications.
Works without touching application code
RelayPlane is a transparent proxy. Point OPENAI_BASE_URL at localhost:4100 and every LLM call from your application, your AI coding assistant, or any third-party tool is automatically captured, logged, and cost-tracked. Datadog LLM Observability requires instrumenting your code with the dd-trace SDK. That means adding imports, wrapping functions, and modifying source files, which is not possible for tools you do not control like Claude Code or Cursor.
Datadog Solves Enterprise Observability Problems. RelayPlane Solves Developer Cost Problems.
Datadog is a genuinely powerful platform for teams that already operate at scale with existing Datadog infrastructure. If your organization monitors servers, containers, and application traces through Datadog, adding LLM observability to the same dashboards and alert policies makes operational sense. APM correlation, existing RBAC, and compliance certifications are real advantages for enterprise teams already in the Datadog ecosystem.
But if you are a Node.js developer, an AI agent builder, or a team without an existing Datadog deployment, Datadog LLM Observability is not the right starting point. The setup overhead (agent installation, SDK instrumentation, account configuration, and enterprise pricing) is disproportionate to the goal of understanding what your LLM calls cost. RelayPlane installs in one npm command, requires zero code changes, runs on localhost, and stores every request log in a local SQLite file you own. No agent. No account. No cloud.
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