System Design Architectures

Interactive technical blueprints, capacity estimates, database sharding strategies, and visual flowcharts for the top 30 system design interview questions.

Target Architectures
AI Agent Architecture Blueprint

Corrective Agentic RAG with Self-Reflection

Autonomous retrieval pipeline combining dense vector embeddings, knowledge graph traversal, and an iterative self-correction loop to diagnose and eliminate hallucinations.

1. System Requirements

Functional
  • Decompose complex multi-hop queries into targeted sub-questions with contextual dependency graphs.
  • Perform hybrid retrieval combining dense vector similarity (pgvector/Qdrant), keyword BM25, and entity graph traversal (Neo4j).
  • Grade document relevance autonomously with self-reflection: if chunks lack relevance, rewrite queries or trigger web search tools.
Non-Functional / SLA
  • Zero hallucination tolerance: every generated claim must map directly to an attributed source citation chunk.
  • P95 query response time under 1.8 seconds including reflection and self-correction loops.
  • Automatic fallback to external search tools (MCP Google Search / Tavily) when internal corpora lack coverage.

2. Scale & Resource Estimates

Throughput: 10,000 hybrid queries/minute across 50M document chunks.

Storage & RAM: 120 GB HNSW dense vector index + 45 GB Neo4j graph cluster + 20 GB Redis embedding cache.

3. System API Endpoints

POST /v1/agentic-rag/query
Content-Type: application/json

{
  "query": "How did Q3 cloud infrastructure spend change compared to our original 2025 budget?",
  "max_reflection_hops": 3,
  "confidence_threshold": 0.85
}

Response (200 OK):
{
  "answer": "Cloud infrastructure spend increased by 14.2% in Q3 2025 ($1.37M vs. budgeted $1.20M), primarily driven by GPU cluster provisioning for agent model inference.",
  "citations": [
    { "source": "2025_Q3_Financial_Review.pdf", "page": 14, "chunk_id": "chk-994", "score": 0.94 },
    { "source": "2025_Annual_Operating_Plan.xlsx", "sheet": "CapEx", "chunk_id": "chk-112", "score": 0.91 }
  ],
  "reasoning_trajectory": [
    "Step 1: Extracted budgeted Q3 cloud spend -> $1.20M",
    "Step 2: Extracted actual Q3 cloud spend -> $1.37M",
    "Step 3: Computed variance -> +14.2% ($170,000 increase)"
  ],
  "retrieval_hops": 2
}

4. Database Schema Design

CREATE TABLE rag_chunks (
    chunk_id VARCHAR(64) PRIMARY KEY,
    document_id VARCHAR(64) NOT NULL,
    text_content TEXT NOT NULL,
    embedding VECTOR(1536), -- pgvector HNSW index
    entities TEXT[],
    metadata JSONB,
    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
);

CREATE INDEX idx_rag_hnsw ON rag_chunks USING hnsw (embedding vector_cosine_ops);
CREATE INDEX idx_rag_doc ON rag_chunks(document_id);

5. Interactive High-Level Architecture

graph TD Query["User Multi-Hop Query"] --> Decomposer["Query Decomposer LLM"] Decomposer --> Search["Hybrid Retrieval: Vector, BM25, Graph"] Search --> Grader{"Relevance Grader LLM"} Grader -->|Relevant Score| Generator["Grounded Answer Generator"] Grader -->|Low Score| Rewriter["Query Rewriter / Web Tool Fallback"] Rewriter --> Search Generator --> HallucinationVerifier{"Hallucination Verifier"} HallucinationVerifier -->|Pass| VerifiedOutput["Verified Answer with Citations"] HallucinationVerifier -->|Fail| Generator

6. Scalability Deep Dive & Bottlenecks

Standard Naive RAG is brittle: it blindly injects the top-K retrieved text chunks into the prompt context, leading to hallucinations when chunks are tangential or contradictory. Agentic RAG introduces an active decision loop: an evaluator LLM grades each chunk's relevance. If the chunks fail the relevance threshold, the agent rewrites the search query (query expansion, entity extraction) and issues a secondary retrieval or falls back to live web search tools before drafting the final answer.

7. Production Scaling Strategies

Context Caching: Cache pre-computed embeddings and document index catalogs in memory using pgvector and Qdrant.

Reciprocal Rank Fusion (RRF): Merge rankings from sparse keyword search, dense semantic search, and knowledge graph neighbors with low CPU overhead.

Speculative Verification: Run hallucination checks asynchronously or in parallel with streaming to provide zero perceived latency overhead for end users.

8. Runnable Production Starter Code

Scaffold