Design an AI model inference gateway
PremiumLLM systemHard
- API gateway
- Streaming
- Rate limiting
Quick answer
This LLM system interview question asks you to design an AI model inference gateway. Aim for a design that uses language models to serve users well, then explain retrieval, prompting, serving, evaluation and trade-offs. Interviewers want to see how you control quality, cost and latency, and how you evaluate the results.
The problem
Design an AI Model Inference Gateway for an enterprise platform. Internal applications and external API consumers send natural language prompts to your gateway. The gateway must authenticate the request, dynamically route it to the optimal external Large Language Model (LLM) provider based on cost and availability, stream the generated response back to the client in real-time, and accurately record the token usage for tenant billing.
What must an AI model inference gateway do?
- Authentication & Quota: Verify tenant API keys and block requests if the tenant has exceeded their monthly budget.
- Dynamic Routing & Failover: Route requests to 'Provider A' by default. If 'Provider A' is down or rate-limited, automatically failover to 'Provider B' without failing the client request.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- API gateway
- Streaming
- Rate limiting
- Cost optimization
- Asynchronous processing
- Fault tolerance
How you’ll practise
- Problem framing
- Data and retrieval
- Prompting and orchestration
- Evaluation and safety
- Serving, cost and latency
- Wrap-up
Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.
What do interviewers look for?
In any LLM system design round.
- Defines the user task and what a good answer is
- Explains how relevant context reaches the model
- Plans evaluation before and after launch
- Controls cost and latency with caching and routing
- Covers safety, privacy and abuse
- Handles failures and fallbacks gracefully
Questions people ask about this interview question
- Which design type is this question?
- It is an LLM system question. You design an AI model inference gateway and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Hard. It suits engineers preparing for senior interviews, where you are expected to drive the discussion and go deep on trade-offs.
- What should I cover first?
- Start with the user task, what a good answer looks like and how it will be measured. Agree on scope with the interviewer before you design anything.
- Can I practise it for free?
- It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.
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Updated · Written by the SevyDevy team