RAG Evaluation Metrics Cheat Sheet

A concise RAG evaluation reference organized by retrieval, context, answer, citation, refusal, security, and production metrics, with practical formulas and a minimal release-gate set.

August 1, 2026 · 9 min · 1894 words · Andy SI
Read more

How to Rerank RAG Retrieval Results: From Hybrid Retrieval to Cross-Encoders, Listwise Ranking, and Evidence-Set Selection

A RAG reranking design guide for AI Application Engineers. It distinguishes retrieval fusion, semantic reranking, business ranking, and evidence-set selection, then provides a production-ready default pipeline.

July 29, 2026 · 37 min · 7834 words · Andy SI
Read more

2026 AI Application Engineer Job-Market Tech Stack: A Deep JD Study of Tokyo, Mainland China, and the US

Based on 20 public job descriptions each from mainland China, the United States, and Tokyo, this study maps the hiring stack for AI Application, Agent, and RAG engineers and gives a Tokyo-focused learning and portfolio roadmap.

July 28, 2026 · 28 min · 5931 words · Andy SI
Read more

From Single-Agent to Multi-Agent: A Guide to Robust Sub-Agent System Design

A programmer-oriented guide to Multi-Agent and Sub-Agent system design: when multiple Agents are needed, task decomposition and coordination patterns, context, permissions, reliability, evaluation, and production delivery.

July 27, 2026 · 66 min · 13852 words · Andy SI
Read more

Context Compression for Production AI Agents: From Message Trimming and Tool-Result Cleanup to Hermes Agent's Layered Compaction

This article systematically explains context-compression methods for production AI agents, distinguishing message trimming, tool-result cleanup, artifact externalization, structured summaries, and native compaction. Using Hermes Agent, LangChain v1, and LangGraph v1, it presents a layered implementation and evaluation approach.

July 26, 2026 · 17 min · 3452 words · Andy SI
Read more

Gradient Descent: How Large Language Models Learn to Generate Text from Random Guesses

An intuitive introduction for programmers without a machine-learning background to gradient descent, loss functions, backpropagation, learning rates, and optimizers in LLM training, from next-token prediction through parameter updates.

July 26, 2026 · 15 min · 3174 words · Andy SI
Read more

Which Diagrams Should You Draw Before Coding Starts?

Using a simplified online bookstore as one continuous example, this guide explains the software diagrams commonly used for requirements, business, architecture, data, interaction, and deployment design.

July 18, 2026 · 2 min · 349 words · Andy SI
Read more

Python Event Loop Fundamentals

Starting with asyncio.run(), coroutines, Tasks, and Futures, learn how Python’s event loop schedules waits, timers, and I/O, and where sequential await, concurrent tasks, and blocking code differ.

July 18, 2026 · 14 min · 2973 words · Andy SI
Read more

RAG Retrieval Engineering: From Hybrid Retrieval to Production Governance

A systematic guide to lexical retrieval, dense retrieval, hybrid fusion, reranking, evaluation, observability, and production governance in RAG systems.

July 17, 2026 · 27 min · 5679 words · Andy SI
Read more

Designing Observability and Evaluation for RAG Systems

Explains how to build an observability and evaluation system for RAG that covers runtime execution, retrieval quality, generation quality, and continuous regression testing.

July 17, 2026 · 12 min · 2397 words · Andy SI
Read more