Mock system design interview at Instacart
A live 45-minute round on a question reported in Instacart interviews, run by an AI interviewer that asks one thing at a time, probes what you say, looks at your whiteboard, and weighs what that round is reported to weigh. It ends with a debrief: a score, what was strong, what was missing.
Design DoorDash
Take a food order, get a restaurant to cook it and a courier to arrive just as it is ready, and keep three parties in sync across millions of orders a day.
You will not see the requirements, the numbers or the design before you start. That is the point.
What the Instacart round is reported to look like
45–60 minutes, product-shaped and narrower than at many large companies: one Instacart feature in detail, such as inventory across stores, assigning shoppers to orders, a product catalogue or delivery tracking.
What it weighs
- A database model and the APIs between components, once the boxes are drawn
- Inventory across many stores that is never quite current
- Edge cases, robustness and rush hours, not only the happy path
- Decisions justified concisely, within the time
The common mistake
Staying generic and high level. Prompts are reported to go into one feature in detail, with follow-ups on the database, security and how components talk to each other, so get a simple design up quickly and leave time for them.
From public interview guides and candidate reports, and Instacart’s own interview guidance where it publishes any. Not endorsed by Instacart. The interviewer is an AI running in that style; it is practice, not a prediction.
Start the round
The interviewer’s opening question is free. Answering it is part of Pro. See an example round and its debrief →
The 4 questions this round draws from
Each is reported in Instacart interviews. Pick one to sit, or read its reference design and walk through a strong answer first.
- Design DoorDashTake a food order, get a restaurant to cook it and a courier to arrive just as it is ready, and keep three parties in sync across millions of orders a day.drawn
- Design AmazonA 500 M-product marketplace: product pages at 100 k views/s, carts that never lose an item, and Prime Day checkout without overselling.
- Design a Price TrackerTrack 500 M products' price history and alert 50 M users when a price drops below their target, in time to buy.
- Design PinterestSave images to boards, browse a personalised grid and search by picture: 100 M daily users, 5 B distinct images behind 100 B saves.
Other companies: Anthropic · Google · Meta · Amazon · OpenAI · Microsoft · Uber · DoorDash