How Helicone Works as an LLM Proxy
Helicone operates as a transparent proxy. Instead of your application calling https://api.openai.com/v1 directly, it calls https://oai.helicone.ai/v1, passing your Helicone API key as an additional header. Helicone forwards the request to OpenAI, logs the full request and response pair, and returns the response to your application with no additional latency beyond the network hop to Helicone's infrastructure. The same proxy pattern works for Anthropic, Google Gemini, Cohere, and other providers. Because the integration is a URL and header change rather than an SDK import, you can add Helicone to an existing codebase in minutes without refactoring. This is particularly useful for SpeedMVPs projects where we want observability from the first deployed version rather than adding it as a retrofit. The proxy approach also means Helicone does not affect the behaviour of the LLM calls in any way, only the visibility into them.
Cost Tracking and Budget Alerts
The first thing most founders want to know about their AI product in production is how much it is spending on LLM API calls per day. Helicone provides per-request cost tracking broken down by model, user, and custom property. You can see your total spend, the cost per user or customer organisation, the cost per feature area if you tag requests with custom properties, and cost trends over time. Budget alerts notify you when spend crosses a defined threshold, which prevents unexpected large bills from runaway usage or inefficient prompts. SpeedMVPs configures Helicone cost tracking from day one of deployment, adds custom property headers for key dimensions (user ID, organisation, feature name) so cost can be attributed correctly, and sets initial budget alert thresholds based on expected usage volumes.
Latency Monitoring and Performance Optimisation
LLM latency is highly variable and directly affects user experience. A response that takes 200ms feels instant; a response that takes 8 seconds feels broken. Helicone tracks latency for every request, showing percentile distributions (P50, P90, P99) by model and time period. This lets you identify when a model upgrade has introduced latency regression, which prompts are consistently slow due to large context windows, or when streaming is not behaving as expected. SpeedMVPs uses Helicone latency data to guide prompt optimisation decisions: moving from GPT-4o to GPT-4o Mini for simple classification tasks where the latency reduction matters more than the slight quality difference, or identifying opportunities to reduce context window size without affecting answer quality.
Caching LLM Responses
Helicone includes a built-in semantic caching feature that can return cached responses for LLM queries that are semantically similar to previous queries, even if the exact text is different. This reduces API costs and response latency for AI products where users frequently ask similar questions. The cache can be configured with a similarity threshold to control how aggressively it matches queries. For deterministic queries (where the same input should always produce the same output), Helicone also supports exact-match caching. SpeedMVPs evaluates whether caching is appropriate for your specific use case during the build: caching is highly beneficial for knowledge copilot queries where many users ask similar questions, but inappropriate for personalised generation tasks where each response should be unique.
Request Logging, Prompt Versioning, and Debugging
Helicone logs the full text of every LLM request and response, which is invaluable for debugging production issues. When a user reports that the AI gave an incorrect or strange response, you can look up the exact request in Helicone, see the full prompt that was sent (including all system messages and context), and identify where the prompt construction went wrong. Helicone also supports prompt management, allowing you to version prompts and track performance metrics by prompt version. This is less comprehensive than LangSmith's evaluation features but sufficient for teams that want basic prompt version tracking without the full LangSmith setup. Custom properties on requests allow filtering the log by user, session, or feature to find relevant requests quickly.
GDPR and Data Handling for LLM Logs
Logging the full text of LLM requests raises GDPR considerations if those requests contain personal data. When users submit queries that include their name, email, medical history, or financial information, that personal data is logged in Helicone's infrastructure, which is hosted on servers in the United States. Helicone provides a Data Processing Agreement, and the EU Standard Contractual Clauses apply for GDPR-compliant transfers. SpeedMVPs designs prompt construction to minimise personal data in LLM requests where possible (using anonymised references rather than full personal details) and configures appropriate log retention in Helicone. For regulated industries such as healthcare or finance where logging patient or client data raises additional concerns beyond general GDPR, SpeedMVPs will discuss whether Helicone's self-hosted option or an alternative observability approach is more appropriate.