Life of a Request

High Level architecture

Request Flow

1. User Sends Request: The process begins when a user sends a request to the LiteLLM Proxy Server (Gateway).

2. Virtual Keys: At this stage the Bearer token in the request is checked to ensure it is valid and under it's budget. Here is the list of checks that run for each request

   • 2.1 Check if the Virtual Key exists in Redis Cache or In Memory Cache
   • 2.2 If not in Cache, Lookup Virtual Key in DB

3. Rate Limiting: The MaxParallelRequestsHandler checks the rate limit (rpm/tpm) for the the following components:

   • Global Server Rate Limit
   • Virtual Key Rate Limit
   • User Rate Limit
   • Team Limit

4. LiteLLM proxy_server.py: Contains the /chat/completions and /embeddings endpoints. Requests to these endpoints are sent through the LiteLLM Router

5. LiteLLM Router: The LiteLLM Router handles Load balancing, Fallbacks, Retries for LLM API deployments.

6. litellm.completion() / litellm.embedding(): The litellm Python SDK is used to call the LLM in the OpenAI API format (Translation and parameter mapping)

7. Post-Request Processing: After the response is sent back to the client, the following asynchronous tasks are performed:

   • Logging to LangFuse (logging destination is configurable)
   • The MaxParallelRequestsHandler updates the rpm/tpm usage for the
     • Global Server Rate Limit
     • Virtual Key Rate Limit
     • User Rate Limit
     • Team Limit
   • The _PROXY_track_cost_callback updates spend / usage in the LiteLLM database. Here is everything tracked in the DB per request

Frequently Asked Questions

1. Is a db transaction tied to the lifecycle of request?
   • No, a db transaction is not tied to the lifecycle of a request.
   • The check if a virtual key is valid relies on a DB read if it's not in cache.
   • All other DB transactions are async in background tasks