Enterprise AI Case Study

The enterprise AI case study is the full requirement-to-architecture walkthrough in one lesson (L379) — the requirements (the brief L359: the users L162, the features L359, the non-functional L359, L379), the decisions (the ADRs L361: the model L365, the RAG L349, the cloud L366, L379), and the architecture (the design L379: the front door L267, the engine room L270, the data L268, the security L325, the observability L346, L379) — the loop's (L380) run (L379).

The one-sentence interview answer: "The case study is the loop, run end to end (L379). The requirements (L359): the brief (L359) — the users (L162), the features (L359): the support copilot (L350) with the RAG (L349); and the non-functional (L359): the TTFT (L145) under 2s, the 1M requests (L358), the GDPR (L371). The decisions (L361): the ADRs (L361) — the model (L365): the tiered (L365) with the routing (L155); the RAG (L349): the build (L363) with the pgvector (L183); and the cloud (L366): the AWS (L261) with the Bedrock (L278). The architecture (L379): the design (L379) — the front door (L267): the gateway (L267) with the auth (L319) and the limits (L318); the engine room (L270): the queue (L270) and the workers (L266); the data (L268): the RDS (L268) and the pgvector (L183); the security (L325): the L325 stack (L325) — the guardrails (L281), the isolation (L320), the audit (L322); and the observability (L346): the OTel (L346) with the evals (L341). The walkthrough (L379): the loop's (L380) run (L379) — the brief (L359) to the ADRs (L361) to the architecture (L379) — the case study (L379), the interview's (L379) proof (L379)."

Think of the case study as the architect's portfolio project. The portfolio piece (the case study, L379) documents the whole project (L379): the client's brief (the requirements, L359) — the house (L173) they want (L359); the design decisions (the ADRs, L361) — the materials (L361) and the layout (L361); and the blueprints (the architecture, L379) — the floors (L379) and the systems (L379). The architect (L379) walks the reviewer (the interviewer, L379) through (L379): the brief (L359), the choices (L361), and the design (L379) — the why (L367) at each (L379). The portfolio works because the arc is complete: the brief, the decisions, and the design (L379).

   the portfolio piece (the case study, L379)
   ┌────────────────────────────────────────────────────────┐
   │ the brief (the requirements, L359) — the house (L173)  │
   │ the decisions (the ADRs, L361) — the materials (L361)  │
   │ the blueprints (the architecture, L379) — the systems  │
   │ (L379)                                                 │
   │ the walkthrough (L379) — the why at each (L367)        │
   └────────────────────────────────────────────────────────┘

The mental model is the portfolio piece: the brief, the decisions, and the blueprints (L379).

   1 · THE REQUIREMENTS (L359)
      the users (L162) · the features (L359) · the non-functional (L359)

   2 · THE DECISIONS (L361)
      the model (L365) · the RAG (L349) · the cloud (L366)
      — the ADRs (L361) with the trade-offs (L367)

   3 · THE ARCHITECTURE (L379)
      the front door (L267) · the engine room (L270) · the data (L268)
      the security (L325) · the observability (L346)

   4 · THE DEFENSE (L379)
      the walkthrough (L379) — the why at each (L367)

The flow is the arc: requirements → decisions → architecture → defense (L379).

• The requirements (L359). The brief (L359): the users (L162), the features (L359), the non-functional (L359).
• The decisions (L361). The ADRs (L361): the model (L365), the RAG (L349), the cloud (L366).
• The architecture (L379). The design (L379): the front door (L267), the engine room (L270), the data (L268), the security (L325), the observability (L346).
• The walkthrough (L379). The loop's (L380) run (L379) — the why (L367) at each (L379).

• An interview (L379). The case study (L379) — the loop (L380) run (L379).
• An enterprise engagement (L379). The requirements (L359), the ADRs (L361), the architecture (L379).
• A portfolio (L379). The case study (L379) — the walkthrough (L379).
• A design review (L379). The architecture (L379) — the boundaries (L379) and the trade-offs (L367).
• Anything enterprise (L380). The arc (L379) — the brief, the decisions, the design (L379).

The through-line: the arc is the loop's — the requirements, the decisions, and the architecture (L379).

Say it in four moves:

1. The requirements. "The brief — the users, the features, the non-functional (L359)."
2. The decisions. "The ADRs — the model (L365), the RAG (L349), the cloud (L366)."
3. The architecture. "The front door (L267), the engine room (L270), the data (L268)."
4. The defense. "The why at each (L367)."

• The arc is the loop's (L380). The brief (L359) → the ADRs (L361) → the architecture (L379) — the L380 loop (L380), run (L379).
• The trade-off is the defense's (L367). The named (L367) — the RAG (L349) vs the fine-tuning (L365) — the why (L367) at each (L379).
• The boundaries are the architecture's (L379). The front door (L267), the engine room (L270) — the L260 floor plan (L260), enterprise-shaped (L379).
• The security is the stack's (L325). The guardrails (L281), the isolation (L320), the audit (L322) — the L325 stack (L325), in the case (L379).
• The observability is the evals' (L346). The OTel (L346) — the evals (L341) in the CI (L296) — the L346 standard (L346), in the case (L379).

• The pieces without the arc (L379). The Redis (L243) and the SQS (L270) named (L379) without the brief (L359) — the loop (L380) un-run (L379).
• The decision-less (L361). The architecture (L379) without the ADRs (L361) — the why (L367) missing (L379).
• The trade-off-less (L367). The choice (L367) un-named (L379) — the surprise (L367) (L379).
• The security-less (L325). The design (L379) without the guardrails (L281) and the isolation (L320) — the L325 stack (L325) (L379).
• The eval-less (L341). The quality (L341) un-defined (L359) — the success (L341) un-measured (L379).

• Run the arc (L379) — the brief (L359), the ADRs (L361), the architecture (L379).
• Name the trade-offs (L367) — at each decision (L361).
• Bound the parts (L379) — the front door (L267), the engine room (L270).
• Include the security (L325) — the stack (L325) in the design (L379).
• Define the evals (L341) — the success (L341) in the brief (L359).

Q: Walk me through the case study.

A: The loop, run end to end (L379). The requirements — the brief: the users, the features, the non-functional (L359). The decisions — the ADRs: the model (L365), the RAG (L349), the cloud (L366). The architecture — the front door (L267), the engine room (L270), the data (L268). And the defense — the why at each (L367).

Q: What's the architecture?

A: The L260 floor plan (L260), enterprise-shaped (L379): the front door (L267) — the gateway (L267) with the auth (L319) and the limits (L318); the engine room (L270) — the queue (L270) and the workers (L266); the data (L268) — the RDS (L268) and the pgvector (L183); the security (L325) — the guardrails (L281), the isolation (L320), the audit (L322); and the observability (L346) — the OTel (L346) with the evals (L341).

Q: How do you defend the decisions?

A: The ADRs (L361): the trade-off (L367) named (L367) — "the RAG (L349) over the fine-tuning (L365) for the freshness (L335) at the latency's (L333) cost" (L367); the cloud (L366) — the AWS (L261) for the Bedrock (L278); and the model (L365) — the tiered (L365) for the 80/20 (L365). The why (L367) at each (L379).

Q: What's the arc?

A: The loop's (L380) run (L379): the requirements (L359) — the brief (L359) elicited (L359); the decisions (L361) — the ADRs (L361); and the architecture (L379) — the design (L379) with the boundaries (L379). The arc (L379) — the brief to the blueprints — is the interview's (L379) proof (L379).

• What's the arc (L379)?
• What's the architecture (L379)?
• How do you defend the decisions (L361)?
• What's the security (L325)?
• What's the observability (L346)?

The senior read: the stages compose the loop's run (L379).

// The case study (L379) — the arc, run (L379).
// 1 · THE REQUIREMENTS (L359) — the brief (L379).
const brief = {
  users: 'support agents + customers',     // L162
  features: ['support-copilot', 'rag'],    // L350, L349
  nonFunctional: {
    ttft: '< 2s',                          // L145
    scale: '1M requests/day',              // L358
    compliance: 'gdpr',                    // L371
  },
  evals: { groundedness: '>= 0.9' },       // L341, L337
};

// 2 · THE DECISIONS (L361) — the ADRs (L379).
const adrs = [
  { id: 'ADR-001', choice: 'tiered models',        why: 'the 80/20 (L365)' },
  { id: 'ADR-002', choice: 'RAG over fine-tuning', why: 'the freshness (L335)' },
  { id: 'ADR-003', choice: 'AWS + Bedrock',        why: 'the L278 access (L278)' },
];

// 3 · THE ARCHITECTURE (L379) — the floor plan (L260).
const architecture = {
  frontDoor:  'api-gateway',               // L267
  engineRoom: 'sqs + workers',             // L270
  data:       'rds + pgvector',            // L268, L183
  security:   'guardrails + isolation + audit',  // L325, L320
  observability: 'otel + evals',           // L346, L341
};

// 4 · THE DEFENSE (L379) — the why at each (L367).
//   "the RAG (L349) for the freshness (L335) at the latency (L333)"

What the reader must SEE — the arc, run:

  the brief with the evals    → the requirements (L359, L341)
  the three ADRs with the why → the decisions (L361)
  the floor plan              → the architecture (L379)
  the why at each             → the defense (L367)

  The requirements, the decisions, the architecture (L379).

• The arc is the interview's speed (L379). The structured run (L379) — the clear (L379) defense (L379).
• The trade-off is the review's (L367). The named (L367) — the debate (L367) shortened (L379).
• The evals are the quality's (L341). The bar (L341) — the success (L341) measured (L379).
• The observability is the cost's (L346). The OTel (L346) — the per-tenant (L334) attribution (L379).

• The enterprise AI case study = the loop's run (L379): the requirements, the decisions, the architecture.
• The requirements: the brief (L359) — the users, the features, the non-functional (L359).
• The decisions: the ADRs (L361) — the model (L365), the RAG (L349), the cloud (L366).
• The architecture: the front door (L267), the engine room (L270), the data (L268), the security (L325), the observability (L346).
• The walkthrough: the why at each (L367).

ENTERPRISE AI CASE STUDY = the loop, run end to end

1 · THE REQUIREMENTS (L359)
  the brief (L359): the users (L162), the features (L359),
  the non-functional (L359): the TTFT (L145), the scale (L358),
  the compliance (L371)
  the evals (L341) — the bar (L359)

2 · THE DECISIONS (L361)
  the model (L365) — the tiered (L365), the routing (L155)
  the RAG (L349) — the build (L363), the pgvector (L183)
  the cloud (L366) — the AWS (L261), the Bedrock (L278)
  the ADRs (L361) with the trade-offs (L367)

3 · THE ARCHITECTURE (L379)
  the front door (L267) · the engine room (L270) · the data (L268)
  the security (L325) — the guardrails (L281), the isolation (L320),
  the audit (L322)
  the observability (L346) — the OTel (L346), the evals (L341)

4 · THE DEFENSE (L379)
  the why (L367) at each — the walkthrough (L379)

INTERVIEW, 4 MOVES
  1 requirements "the brief (L359)"
  2 decisions    "the ADRs (L361)"
  3 architecture "the floor plan (L379)"
  4 defense      "the why at each (L367)"

You now hold the case study: the requirements, the decisions, the architecture, and the defense — with the brief to the blueprints. The portfolio piece is complete — and the walkthrough is rehearsed (L379).

Next: the capstone — the deliverables, the diagrams, the cost models, and the decision rule (L380).