System design · Free PDF
AI System Design
A framework for the design round and worked cases: support bot, document search, coding agent and more.
System Design for AI Agents
Agent loops, tools, state and memory, permissions, and how agents fail once real users touch them.
Free PDF · sent by email the day it’s ready
Who it’s for
For engineers whose design round includes an agent: a support bot that takes actions, a coding agent, an assistant with tool access.
It pairs with the AI System Design Casebook, which covers the general framework.
What it covers
- Agent loops
- Tools and state
- Permissions
- Failure modes
A question from the guide
One of the 16 questions, with its model answer.
What makes an agent worth building
How would you show that an agent beats a simpler workflow for the same task?
Model answer
Run both against one shared set of realistic tasks and compare five things: task success rate, cost per successful task, latency at p50 and p95, how bad the worst failures are, and maintenance burden. For cost I compare distributions, because agent spend has a long tail. Any one of those can veto the agent.
On well-understood tasks the workflow usually wins on most of them. The agent earns its place on varied, unpredictable tasks where you can't list the steps in advance. A common outcome is to ship the workflow for the main path and route the odd cases to an agent. I keep both harnesses runnable and re-run the comparison when models or prices change. One more tell: if an agent's traces show the same tool sequence every run, it's a workflow paying agent overhead.
- What they’re checking:
- Whether you treat "should this be an agent?" as a measurement against a baseline instead of a preference.
- Likely follow-up:
- Which of those five would you weigh most for a customer-facing feature, and why?
See all 16 questions: Agentic AI Interview Questions and Answers →
What the guide will include
A framework for the round
Requirements, architecture, tradeoffs, evaluation and failure modes, in the order you say them.
Worked designs
Prompts worked end to end the way you would answer them at the whiteboard, with the diagram.
Tradeoffs to name
The choices interviewers push on, and what each option costs in latency, money and risk.
Failure modes and evals
How the system breaks in production, how you would notice, and what you would measure.
A PDF you can print
Read it on your phone before the call, or print the sections you want to drill.
Planned contents
The guide isn’t out yet, so chapters and their order may still change.
- 1. How the design round runs
- 2. Agent loops
- 3. Tools and state
- 4. Permissions
- 5. Failure modes
- 6. Practice prompts
Free PDF
All 16 questions with model answers
A model answer for every question, what the interviewer is checking, the follow-up and the mistake to avoid.
Questions about the guide
Is the PDF really free?
Yes. Leave your email and we send the PDF the day it is ready. No payment details, and every email has a one-click unsubscribe link.
How is it different from the questions page?
The questions page lists every question with a handful of sample answers. The PDF has a model answer for each question, plus what the interviewer is checking, the likely follow-up and the mistake to avoid.
Is it based on a specific company’s interviews?
No. It is written from the concepts the role or system depends on. We don’t name companies or claim to know what any one company asks.
When will it be ready?
It isn’t out yet. Leave your email and we send it the day it is; nothing else arrives before then.
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