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Your agent reads customer emails, queries a private database, and can send messages. Harden it against prompt injection.

This is the lethal trifecta in one sentence, and most candidates reach for a better system prompt. The answer that scores breaks the trifecta architecturally, because no amount of prompting stops indirect injection once all three capabilities are present.

Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.

This is the lethal trifecta in one sentence, and most candidates reach for a better system prompt. The answer that scores breaks the trifecta architecturally, because no amount of prompting stops indirect injection once all three capabilities are present.

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Next in this trackYour agent platform calls each customer's Salesforce, Slack, and email on their behalf. Design credential isolation.PremiumNext in this trackAn agentic loop runs forever on long-horizon tasks. Propose an algorithmic change to stop the looping and evaluate it offline.PremiumNext in this trackDesign a Graph-RAG pipeline that turns a question into Cypher, runs it, and heals its own broken queries.Premium
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