Real-World Case Studies
How OpenAI Deep Research, Claude Code, Perplexity, Cursor, and Devin work under the hood. Production architecture breakdowns with design decisions for interviews.
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After this section you can
- Explain how five production agentic systems (Deep Research, Claude Code, Perplexity, Cursor, Devin) are actually built and name the design decision each one demonstrates
- Contrast the model-first, architecture-first, and orchestration-first schools and argue which fits a given problem
- Recognize the agentic anti-pattern (unbounded autonomy) and name the guardrail and layer that would have contained it
- Cite a production precedent by name in an interview instead of inventing an architecture from scratch
Real-World Agentic Architectures
How five of the most impactful AI products actually work under the hood — with the architecture decisions and metrics you can quote in an interview.
OpenAI Deep Research, Claude Code, Perplexity, Cursor, and Devin look like five different products, but under the hood they reuse a small set of patterns: tiered model routing, execution isolation, action classification, a self-correction loop, and a human gate for risky actions. Learn the patterns, not the trivia — then you can reason about any agentic product an interviewer throws at you.
Below, each case study leads with the one architectural idea it made famous, shows how the pieces fit together, and ends with the line you can actually use in an interview. First, the lay of the land: