# System Design Newsletter

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## API testing techniques, including fuzz, penetration, and injection attack testing

DevFeed: [API testing techniques, including fuzz, penetration, and injection attack testing](<https://devfeed.tech/articles/api-testing-was-hard-until-i-learned-these-53-techniques-17925.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/types-of-api-testing>)

Author: Neo Kim

Published: 2026-09-07T16:59:35Z

Content type: article

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [API](<https://devfeed.tech/topics/api.md>), [Testing](<https://devfeed.tech/topics/testing.md>)

Tags: [api](<https://devfeed.tech/tags/api.md>), [api-testing](<https://devfeed.tech/tags/api-testing.md>), [testing](<https://devfeed.tech/tags/testing.md>)

### AI overview

Part 2 covers API testing techniques, including fuzz testing, penetration testing, injection attack testing, and 25 other techniques.

### Source excerpt

#175: Part 2 - fuzz testing, penetration testing, injection attack testing, and 25 others.

## System design tradeoffs for scalable, reliable systems

DevFeed: [System design tradeoffs for scalable, reliable systems](<https://devfeed.tech/articles/50-shades-of-system-design-17924.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/system-design-tradeoffs>)

Author: Neo Kim

Published: 2026-09-03T12:17:25Z

Content type: article

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [systems](<https://devfeed.tech/topics/systems.md>)

Tags: [systems](<https://devfeed.tech/tags/systems.md>)

### AI overview

An article about the tradeoffs involved in designing scalable, reliable systems.

### Source excerpt

#174: tradeoffs behind designing scalable, reliable systems

## API Testing Techniques Including Smoke, Functional, and Unit Testing

DevFeed: [API Testing Techniques Including Smoke, Functional, and Unit Testing](<https://devfeed.tech/articles/i-struggled-with-api-testing-until-i-learned-these-53-techniques-17908.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/api-testing-types>)

Author: Neo Kim

Published: 2026-08-31T11:19:11Z

Content type: article

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [API](<https://devfeed.tech/topics/api.md>), [Testing](<https://devfeed.tech/topics/testing.md>), [Unit testing](<https://devfeed.tech/topics/unit-testing.md>)

Tags: [api](<https://devfeed.tech/tags/api.md>), [api-testing](<https://devfeed.tech/tags/api-testing.md>), [techniques](<https://devfeed.tech/tags/techniques.md>), [testing](<https://devfeed.tech/tags/testing.md>), [unit-testing](<https://devfeed.tech/tags/unit-testing.md>)

### AI overview

This article covers API testing techniques, including smoke testing, functional testing, unit testing, and 22 other techniques.

### Source excerpt

#173: Part 1 - smoke testing, functional testing, unit testing, and 22 others.

## A Guide to Fine-Tuning Large Language Models

DevFeed: [A Guide to Fine-Tuning Large Language Models](<https://devfeed.tech/articles/fine-tuning-a-deep-dive-17920.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/llm-fine-tuning-guide-with-lora-and-qlora>)

Author: Neo Kim

Published: 2026-08-24T16:23:10Z

Content type: tutorial

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [Fine-tuning](<https://devfeed.tech/topics/fine-tuning.md>), [Large Language Model](<https://devfeed.tech/topics/llm.md>)

Tags: [deep-dive](<https://devfeed.tech/tags/deep-dive.md>), [fine-tuning](<https://devfeed.tech/tags/fine-tuning.md>), [guide](<https://devfeed.tech/tags/guide.md>), [llms](<https://devfeed.tech/tags/llms.md>)

### AI overview

This article is presented as a guide to fine-tuning large language models.

### Source excerpt

#171: The Fine-Tuning Guide That Will Change How You Build With LLMs

## How to Build AI Agents That Don't Start Over When They Fail

DevFeed: [How to Build AI Agents That Don't Start Over When They Fail](<https://devfeed.tech/articles/how-to-build-ai-agents-that-don-t-start-over-when-they-fail-17911.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/durable-ai-agents>)

Author: Neo Kim

Published: 2026-08-20T17:26:04Z

Content type: tutorial

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [AI Agent](<https://devfeed.tech/topics/ai-agent.md>), [Artificial Intelligence](<https://devfeed.tech/topics/ai.md>)

Tags: [agents](<https://devfeed.tech/tags/agents.md>), [ai-agent](<https://devfeed.tech/tags/ai-agent.md>), [ai-agents](<https://devfeed.tech/tags/ai-agents.md>), [build](<https://devfeed.tech/tags/build.md>), [how-to](<https://devfeed.tech/tags/how-to.md>), [workflow](<https://devfeed.tech/tags/workflow.md>)

### AI overview

This tutorial explains why long-running AI agent workflows need durable execution. It describes how tracking completed steps can let a workflow resume after failures, retries, waits for human approval, or loss of the process running it, using Inngest as a case study.

### Source excerpt

#170: The Infrastructure AI Agents Actually Need

## How to Build an AI Research Agent

DevFeed: [How to Build an AI Research Agent](<https://devfeed.tech/articles/how-to-build-an-ai-research-agent-17917.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/how-to-build-an-ai-research-agent-with-mcp>)

Author: Louis-François Bouchard

Published: 2026-08-10T11:52:40Z

Content type: tutorial

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [Artificial Intelligence](<https://devfeed.tech/topics/ai.md>), [Generative AI](<https://devfeed.tech/topics/generative-ai.md>)

Tags: [agent](<https://devfeed.tech/tags/agent.md>), [ai](<https://devfeed.tech/tags/ai.md>), [generative-ai](<https://devfeed.tech/tags/generative-ai.md>), [how-to](<https://devfeed.tech/tags/how-to.md>), [masterclass](<https://devfeed.tech/tags/masterclass.md>)

### AI overview

A tutorial about building an AI research agent, presented as part of a Generative AI Masterclass.

### Source excerpt

#168: Part 5 - Generative AI Masterclass

## Vertical Small LLMs: A Deep Dive

DevFeed: [Vertical Small LLMs: A Deep Dive](<https://devfeed.tech/articles/vertical-small-llms-a-deep-dive-17913.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/fine-tuning-small-language-models>)

Author: Neo Kim

Published: 2026-08-03T10:27:31Z

Content type: tutorial

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [Large Language Model](<https://devfeed.tech/topics/llm.md>)

Tags: [build](<https://devfeed.tech/tags/build.md>), [deep-dive](<https://devfeed.tech/tags/deep-dive.md>), [how-to](<https://devfeed.tech/tags/how-to.md>), [llms](<https://devfeed.tech/tags/llms.md>), [model](<https://devfeed.tech/tags/model.md>), [models](<https://devfeed.tech/tags/models.md>), [parameter](<https://devfeed.tech/tags/parameter.md>)

### AI overview

A deep dive into vertical small language models, including how a fine-tuned 3-billion-parameter model can outperform frontier models for a specific job and how to build one.

### Source excerpt

#166: How a fine-tuned 3-billion-parameter model beats today's frontier models at one job, and how to build one this weekend

## A field guide to splitting systems, keeping data correct, and surviving failure in production

DevFeed: [A field guide to splitting systems, keeping data correct, and surviving failure in production](<https://devfeed.tech/articles/i-struggled-with-microservices-until-i-learned-these-22-patterns-17921.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/microservices-design-patterns>)

Author: Neo Kim

Published: 2026-07-23T10:24:07Z

Content type: tutorial

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [Microservice](<https://devfeed.tech/topics/microservice.md>), [Microservices](<https://devfeed.tech/topics/microservices.md>), [Architecture & Design](<https://devfeed.tech/topics/architecture-design.md>), [systems](<https://devfeed.tech/topics/systems.md>)

Tags: [data](<https://devfeed.tech/tags/data.md>), [microservices](<https://devfeed.tech/tags/microservices.md>), [patterns](<https://devfeed.tech/tags/patterns.md>), [production](<https://devfeed.tech/tags/production.md>), [systems](<https://devfeed.tech/tags/systems.md>)

### AI overview

This field guide covers microservices design patterns for splitting systems, maintaining data correctness, and handling failures in production.

### Source excerpt

#164: A field guide to splitting systems, keeping data correct, and surviving failure in production

## Using NotebookLM as a Grounded Knowledge Layer for PR Reviews, Design Reviews, Debugging, and Onboarding

DevFeed: [Using NotebookLM as a Grounded Knowledge Layer for PR Reviews, Design Reviews, Debugging, and Onboarding](<https://devfeed.tech/articles/what-happens-when-your-coding-agent-actually-knows-your-architecture-17918.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/how-to-use-notebooklm>)

Author: Neo Kim

Published: 2026-07-20T11:31:27Z

Content type: article

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [coding](<https://devfeed.tech/topics/coding.md>), [Pull Request](<https://devfeed.tech/topics/pull-request.md>), [debugging](<https://devfeed.tech/topics/debugging.md>), [Tooling](<https://devfeed.tech/topics/tooling.md>)

Tags: [architecture](<https://devfeed.tech/tags/architecture.md>), [coding](<https://devfeed.tech/tags/coding.md>), [debugging](<https://devfeed.tech/tags/debugging.md>), [onboarding](<https://devfeed.tech/tags/onboarding.md>), [reviews](<https://devfeed.tech/tags/reviews.md>)

### AI overview

The article describes using NotebookLM as a grounded knowledge layer for PR reviews, design reviews, debugging, and onboarding.

### Source excerpt

#163: How I turned NotebookLM into a grounded knowledge layer for PR reviews, design reviews, debugging, and onboarding

## How to Build a Domain Expert AI

DevFeed: [How to Build a Domain Expert AI](<https://devfeed.tech/articles/how-to-build-a-domain-expert-ai-17912.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/fine-tuning-ai-models>)

Author: Louis-François Bouchard

Published: 2026-07-17T11:00:54Z

Content type: tutorial

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [Generative AI](<https://devfeed.tech/topics/generative-ai.md>), [Artificial Intelligence](<https://devfeed.tech/topics/ai.md>)

Tags: [ai](<https://devfeed.tech/tags/ai.md>), [generative](<https://devfeed.tech/tags/generative.md>), [generative-ai](<https://devfeed.tech/tags/generative-ai.md>), [how-to](<https://devfeed.tech/tags/how-to.md>), [masterclass](<https://devfeed.tech/tags/masterclass.md>)

### AI overview

Part 4 of a Generative AI Masterclass about how to build a domain expert AI.

### Source excerpt

#162: Part 4 - Generative AI Masterclass

## Graph-Shaped Shared Memory for AI Agents

DevFeed: [Graph-Shaped Shared Memory for AI Agents](<https://devfeed.tech/articles/how-to-use-ai-agents-better-than-99-of-people-17914.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/graph-based-agent-memory>)

Author: Neo Kim

Published: 2026-07-07T11:32:10Z

Content type: tutorial

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [AI Agent](<https://devfeed.tech/topics/ai-agent.md>), [Graphs](<https://devfeed.tech/topics/graphs.md>), [graph-database](<https://devfeed.tech/topics/graph-database.md>), [Amazon S3](<https://devfeed.tech/topics/amazon-s3.md>), [Retrieval Augmented Generation (RAG)](<https://devfeed.tech/topics/retrieval-augmented-generation-rag.md>), [Open Source](<https://devfeed.tech/topics/open-source.md>)

Tags: [ai-agent](<https://devfeed.tech/tags/ai-agent.md>), [ai-agents](<https://devfeed.tech/tags/ai-agents.md>), [amazon-s3](<https://devfeed.tech/tags/amazon-s3.md>), [graph](<https://devfeed.tech/tags/graph.md>), [graph-database](<https://devfeed.tech/tags/graph-database.md>), [open-source](<https://devfeed.tech/tags/open-source.md>), [rag](<https://devfeed.tech/tags/rag.md>)

### AI overview

A guide to shared memory for multiple AI agents, using Omnigraph as a case study. It explains why shared folders and vector databases can fail, how graph-shaped memory represents knowledge, and how transactions, versioning, and combined retrieval methods can help agents share context.

### Source excerpt

#160: A full guide to graph shaped memory for AI agents

## Content Delivery Network (CDN) - A Deep Dive

DevFeed: [Content Delivery Network (CDN) - A Deep Dive](<https://devfeed.tech/articles/content-delivery-network-cdn-a-deep-dive-17916.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/how-does-cdn-work>)

Author: Neo Kim

Published: 2026-07-02T20:18:06Z

Content type: tutorial

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [Network](<https://devfeed.tech/topics/network.md>)

Tags: [concepts](<https://devfeed.tech/tags/concepts.md>), [deep-dive](<https://devfeed.tech/tags/deep-dive.md>), [introduction](<https://devfeed.tech/tags/introduction.md>), [network](<https://devfeed.tech/tags/network.md>)

### AI overview

An introduction to content delivery networks and their core concepts.

### Source excerpt

#159: A clear introduction to CDNs and their core concepts

## A2A Protocol - Deep Dive

DevFeed: [A2A Protocol - Deep Dive](<https://devfeed.tech/articles/a2a-protocol-deep-dive-17906.md>)

Original publisher: [Read original article](<https://newsletter.systemdesign.one/p/agent-to-agent-protocol>)

Author: Eric Roby

Published: 2026-06-26T13:43:17Z

Content type: article

Language: en

Sources: [System Design Newsletter](<https://devfeed.tech/sources/system-design-newsletter.md>)

Topics: [Protocol (disambiguation)](<https://devfeed.tech/topics/protocol.md>), [Artificial Intelligence](<https://devfeed.tech/topics/ai.md>)

Tags: [a2a](<https://devfeed.tech/tags/a2a.md>), [a2a-protocol](<https://devfeed.tech/tags/a2a-protocol.md>), [agents](<https://devfeed.tech/tags/agents.md>), [ai](<https://devfeed.tech/tags/ai.md>), [ai-agents](<https://devfeed.tech/tags/ai-agents.md>), [deep-dive](<https://devfeed.tech/tags/deep-dive.md>), [protocol](<https://devfeed.tech/tags/protocol.md>)

### AI overview

A deep dive into the A2A Protocol and how AI agents collaborate to solve complex tasks.

### Source excerpt

#158: How AI agents collaborate to solve complex tasks