Architectural Case Study

Legal Retrieval and Semantic Search Engine

Hybrid semantic search and document retrieval engine for litigation records

Engineering Lead & Systems Architect
Led 10-person cross-functional engineering team (1 UI/UX, 1 FE, 1 BE, 2 ML, 1 DevOps/SRE, 1 PM, 2 QA, 1 BA)
2024-2025
System Specification // LEGAL-RETRIEVAL-SEMANTIC-SEARCH-ENGINE
PRODUCTION ARCHITECTURE
Architectural Mandate & Scope

Engineered a specialized document retrieval and semantic search engine for law firms. The platform processes high-volume court filings and scanned briefs via asynchronous OCR, uses hybrid retrieval combining Pinecone dense vector indexing with OpenSearch lexical search, and enforces cross-encoder reranking with strict page-level citation validation to eliminate hallucinations.

Quantified Telemetry & Performance Baselines
search Latency
Sub-1.2s hybrid retrieval and reranking
citation Accuracy
100% verified source text page attribution
ingestion Throughput
Multi-page legal briefs OCR-parsed asynchronously
index Coverage
Hybrid lexical and dense vector representation
Engineered Technology Stack
PythonFastAPIPostgreSQLPineconeOpenSearchCeleryRedisTesseract OCRCohere RerankDocker
Topology:AI & Search Systems
Deployment:Legal Technology & Litigation Practice
Cycle:8 months delivery
Leadership & Engineering Organization

Engineering team structure and leadership.

How the engineering organization was structured, staffed across disciplines, and directed through delivery.

Leadership Mandate
Engineering Lead & Systems Architect
10-Person Multidisciplinary Engineering Team Directed by Yogesh
Cross-Functional Discipline Matrix
8 Specialized Functional Pods
Machine Learning & Retrieval2 ML Engineers

Dense vector embeddings, Pinecone indexing, and Cohere cross-encoder reranker tuning

Backend Architecture1 Backend Architect

Python FastAPI query layer, PostgreSQL metadata schema, and low-latency API contracts

Async Ingestion & OCR1 Systems Engineer

Celery and Redis worker pipelines, Tesseract OCR parsing, and legal document chunking

Frontend Engineering1 Frontend Engineer

Legal researcher interface, document previewer, and verified citation coordinate navigation

Product UI/UX Design1 Product Designer

Litigation discovery workflows, citation inspection UI, and legal search user experience

DevOps & Infrastructure1 SRE

Docker containerization, AWS ECS cluster management, and secure document store access

QA & Verification Automation2 QA Engineers

Automated regression suites, citation accuracy verification tests, and query latency benchmarks

Product & Legal Domain Analysis2 PM / BA

Legal domain requirements, citation compliance, case law taxonomy, and statutory mapping

Direct Architectural Contributions & Critical Paths
Personally Engineered & Directed
01

Led the 10-person multidisciplinary engineering team across ML, backend, QA, and infrastructure from architectural concept to delivery

02

Architected the hybrid search pipeline pairing Pinecone dense vector indexing with OpenSearch lexical BM25 matching

03

Designed the asynchronous background ingestion architecture using Celery, Redis, and Tesseract OCR for high-volume scanned court briefs

04

Engineered structural chunking strategies that respect legal boundaries (statutes, clauses, citations) rather than fixed token splits

05

Implemented cross-encoder reranking and citation validation guaranteeing direct source page coordinates for every retrieved result

System Benchmarks & Outcomes

Measured operational outcomes.

Concrete reliability benchmarks and performance metrics delivered to production.

Metric 01
Sub-1.2s hybrid retrieval and reranking

Search Latency

Metric 02
100% verified source text page attribution

Citation Accuracy

Metric 03
Multi-page legal briefs OCR-parsed asynchronously

Ingestion Throughput

Metric 04
Hybrid lexical and dense vector representation

Index Coverage

Technical Execution

Architectural decisions & implementation.

Target Architecture & Implementation

How the system was designed, structured, and deployed

Engineered an asynchronous ingestion pipeline with Celery and Redis that handles document OCR, text extraction (PyPDF / Unstructured), and custom structural chunking that preserves statutes, legal clauses, and citation boundaries. Implemented a hybrid search engine combining PostgreSQL for structured relational metadata, Pinecone for dense semantic vector search, and OpenSearch for lexical BM25 matching. Integrated a cross-encoder reranker to refine top candidate passages, backed by an attribution engine that mandates exact source page coordinates for every retrieved result.

System Component & Infrastructure Ledger

Detailed breakdown of runtime dependencies, protocols, and architectural roles

9 Core Subsystems
01
Python and FastAPI

High-performance query execution and REST endpoints

02
PostgreSQL

Relational case records, metadata, and citation mappings

03
Pinecone

Managed high-dimensional dense vector indexing and similarity search

04
OpenSearch

Inverted index BM25 lexical keyword matching

05
Celery workers with Redis broker

Background OCR and PDF chunking

06
Tesseract OCR and PyPDF

Text extraction from degraded legal scans

07
Cohere cross-encoder reranker

Precision candidate scoring

08
Docker containerization

Reproducible deployments across staging and cloud

09
AWS S3

Encrypted document and court record storage

"The search engine turned days of discovery review into minutes. Being able to jump directly from a search result to the highlighted paragraph on page 84 of an original court filing gave our legal team absolute confidence."
MP
Managing Partner, Litigation Chambers

Legal Technology & Litigation Practice