Index Design: Vector, Hybrid, Keyword, Metadata Retrieval systems feel magical when they work and brittle when they do not. The difference is rarely “better AI” in the abstract. It is usually index design: how content is represented, stored, filtered, and searched so that a query can produce strong candidates fast enough to be useful. The […]

Vector Database Indexes: HNSW, IVF, PQ, and the Latency-Recall Frontier Vector databases exist because “nearest neighbor” is easy to say and expensive to do at scale. The moment you have millions of vectors, high dimensionality, filters, and real latency targets, brute force similarity becomes a cost sink. Indexes are the bridge between semantic search as […]

Tool-Based Verification: Calculators, Databases, APIs The most valuable shift in applied AI is not that models can talk. It is that models can participate in workflows where truth is checked outside the model. Tool-based verification turns language generation into a controlled interface layer. Instead of trusting a model’s internal guess about a number, a record, […]

Semantic Caching for Retrieval: Reuse, Invalidation, and Cost Control Retrieval systems tend to become expensive for the same reason they become useful: they get called everywhere. Once retrieval is the default way to ground answers, power assistants, and surface organizational knowledge, the traffic pattern changes. The system starts receiving repeated questions, near-duplicates, and variations that […]

Retrieval Evaluation: Recall, Precision, Faithfulness Retrieval is the part of an AI system that decides what the model is allowed to know in the moment. If retrieval fails, a grounded system becomes an ungrounded system, even if the language model is strong. That is why retrieval evaluation is not a side task. It is a […]

Reranking and Citation Selection Logic Retrieval systems succeed or fail in the space between “candidate generation” and “final evidence.” Candidate generation is designed to be fast and broad. It prefers recall, often returning passages that are merely related, not necessarily decisive. Reranking is the step that restores precision. It is the stage where the system […]

RAG Architectures: Simple, Multi-Hop, Graph-Assisted Retrieval-augmented generation is a system pattern: generate answers with evidence that the system retrieves. The most important word is “system.” Success depends less on any single model and more on how retrieval, ranking, context construction, and answer synthesis cooperate under real constraints. When this cooperation is weak, the model fills […]

Query Rewriting and Retrieval Augmentation Patterns A retrieval system is a translator between human intent and an index. People ask for “the thing I mean,” not “the token sequence that matches your data store.” Query rewriting exists because natural language is flexible and indexes are literal. The goal is not to rewrite for its own […]

Provenance Tracking and Source Attribution A retrieval system is only as trustworthy as its ability to answer one question: where did this come from? When a system produces an answer that influences decisions, the user needs more than fluent language. They need a trail. Provenance is that trail. It is the structured record of where […]

PII Handling and Redaction in Corpora A retrieval corpus is a memory surface. If it contains sensitive personal data, the system can surface that data unintentionally through search results, citations, summaries, or tool-assisted workflows. That is why handling personally identifiable information is not only a compliance checkbox. It is an engineering requirement that shapes ingestion, […]

Permissioning and Access Control in Retrieval Retrieval systems are readers. In many products, they are also gatekeepers. The system decides which documents are eligible to be retrieved, which passages can be cited, and which facts can be asserted. If the permission model is weak, retrieval becomes a leakage engine. It can surface content from the […]

PDF and Table Extraction Strategies PDF is one of the most common knowledge containers in the world, and one of the least honest. It looks like a document, so people assume it behaves like a document. Under the hood it is closer to a set of drawing instructions: place this glyph at these coordinates, draw […]