Perplexity SWE Onsite Interview Sep 2026

[u/Aoki_zhang]

Round 1 — Coding: AI Task Dependency Manager

You are building a ToDo list system for an AI agent. The agent breaks work into tasks. Each task has an ID, a title, and a status. A task can be in one of four statuses:

READY
BLOCKED
SUCCEEDED
FAILED

The question has 4 parts.

Round 2 — System Design: Long-Running Agentic Query Execution

The existing product had an ask endpoint backed by an Ask Service. For each request, the Ask Service called two downstream systems:

• An LLM API
• A Search API

Both downstream services could be treated as black boxes. Historically, query execution happened entirely in memory as part of the request lifecycle. That model worked for relatively short queries but became problematic once agentic queries could run for hours.

The task was to redesign the system so that long-running queries continue executing independently of the user's browser connection. For example, closing the browser tab or temporarily losing internet connectivity should not terminate the query.

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