Level Up Coding System Design Newsletter

What OpenAI’s Data Agent Teaches Us About Building Reliable AI Agents

How OpenAI built its data agent to work across 70,000 datasets.

Aug 2 • Nikki Siapno

11

1

July 2026

Vector Databases Clearly Explained

The mental model that makes vector databases click.

Jul 25 • Nikki Siapno

25

1

3

What Netflix Live Teaches Us About Building Reliable Systems

How does Netflix stream live events without crashing?

Jul 18 • Nikki Siapno

21

3

RAG Clearly Explained

The mental model every engineer should have.

Jul 15 • Nikki Siapno

39

2

7

How Discord Fans Out One Message to a Million Users

A case study in fanout, bottlenecks, and the engineering decisions behind Discord's scale.

Jul 7 • Nikki Siapno

24

1

2

June 2026

LLMs: The Essential Guide

Most engineers only see the API layer. Here's what's happening underneath.

Jun 26 • Nikki Siapno

41

4

MCP Clearly Explained

Plus: Big upgrades are coming to LUC. Vote on what you'd like to see first.

Jun 15 • Nikki Siapno

48

3

5

May 2026

REST vs GraphQL vs gRPC

The tradeoffs behind resource-driven, query-driven, and method-driven APIs.

May 28 • Nikki Siapno

37

7

Service Discovery in Distributed Systems Clearly Explained

How modern systems dynamically locate healthy services as infrastructure constantly changes.

May 13 • Nikki Siapno

18

2

Docker vs Kubernetes

(4 min read) | The real difference that actually matters, how to decide, where teams go wrong, and more...

May 11 • Nikki Siapno

37

2

3

OAuth Clearly Explained

(4 min read) | OAuth flow, three different tokens, three different jobs, what OAuth actually solves, where OAuth systems usually break, and more

May 1 • Nikki Siapno

140

1

18

April 2026

Infrastructure as Code Clearly Explained

The IaC workflow that actually works, why it matters in practice, security risks you can't ignore, and more...

Apr 27 • Nikki Siapno

19

3