1.3 — Selecting Architectural Patterns

CCAR-P Domain 1 · Task 1.3

What You Need to Know

Three Tiers (Anthropic)

Tier	Description	When
Augmented LLM	Single model call + retrieval/tools/memory	Default for most problems
Workflow	Predefined code paths orchestrate LLMs + tools	Steps known; need predictability, auditability
Agent	Model dynamically directs its own processes/tools	Path cannot be scripted

Five Workflow Patterns

Pattern	Selection cue
Prompt chaining	Task decomposes into fixed sequential subtasks
Routing	Distinct input categories better handled separately
Parallelisation	Independent subtasks or multiple perspectives (sectioning / voting)
Orchestrator-workers	Subtasks cannot be predicted in advance
Evaluator-optimizer	Clear evaluation criteria exist and iteration helps

Decision Rule

Find the simplest solution that meets requirements; add complexity only when it demonstrably improves outcomes. Escalate tier only when the simpler tier cannot meet a named requirement.

Key Concept: Workflows beat agents when steps are known. Agents earn cost when the path cannot be scripted.

Exam Traps

• Deploying an autonomous agent for a fixed, well-specified pipeline
• Choosing chaining when the scenario describes distinct categories (want routing)
• Choosing evaluator-optimizer with no clear evaluation criteria
• One monolithic prompt for a task that needs staged quality gates