Latent Health Senior+ Software Engineer Interview Experience — A 45-Minute System Design Screen on Prior Authorization Workflows

Role: Software Engineer (interviewer said they're targeting senior level)
Round: System design phone screen
Duration: 45 minutes (~5 min intros, ~35 min design, ~5 min candidate Q&A)
Format: Screen share + Excalidraw (bring your own whiteboard tool — have a link ready)

Background (given by the interviewer, ~4 minutes)

Latent Health's first product is in the prior authorization (PA) space. The interviewer walks through the domain first:

When a doctor prescribes a medication, the prescription is sent to the pharmacy the patient chooses. The pharmacy then checks with the patient's insurance payer. If the payer wants more justification before agreeing to pay, it requires a prior authorization form to be submitted.

At that point a pharmacist (or the doctor) has to dig through the patient's records, pull out the relevant clinical information, and fill out the form to justify why the patient needs this medication. The form goes to the insurance company, which checks it against their policy and either approves or denies it. Sometimes there is back-and-forth — the payer asks for more information and the form has to be resubmitted.

These delays mean sick patients wait longer for medication their doctor already prescribed.

Latent's platform sits between the pharmacy and the insurance company. When it detects a PA is required, it pulls up the correct forms for that specific payer and uses AI to auto-fill them from the patient's records. The pharmacist logs into Latent, reviews the pre-filled form, makes any edits, and sends it off. Latent is responsible for getting the payer's response back reliably and quickly.

The actual task

Assume the platform above is already built. You are designing three new features to add to it.

1. Get the status of a prior authorization.
2. A pharmacist can add a prior authorization to their worklist. ("Like engineers assigning tickets to themselves — pharmacists assign PAs to themselves.")
3. End-of-day digest email. At the end of a pharmacist's workday, they receive an email listing the PAs they need to look at — ones that changed in a meaningful way, or that are stale (no update in a day).

Scale (given when asked)

Clarifications the interviewer gave during the round

• The PA record is created by Latent, not by the user. Latent creates it when it sees a message from the insurance company that a PA is required.
• From there: the pharmacist reviews the AI-filled form → may edit it → approves it to be sent → it goes to the insurance company → the insurance company responds asynchronously, so you need some way to receive that external response.
• The users are pharmacists, not doctors. (Worth repeating — it's easy to conflate the two given the domain intro.)
• Auth is out of scope. Assume an existing auth service handles user authentication/authorization.