First Principles Design: How Top Engineers Rethink System Architecture

First Principles Thinking in Software Design

First principles thinking means breaking a problem down to what must be true before deciding how to implement anything. This article collects design philosophies from ten experienced engineers who apply this approach to system design, compiler infrastructure, observability, and architecture.

1. Chris Lattner: Design from Fundamental Problems

Chris Lattner, creator of LLVM, emphasizes tracing problems to their root. His approach: identify the fundamental problems a system still faces, then design from the ground up to solve them. During LLVM's inception (Christmas 2000), he asked what core properties a compiler framework must have to support future languages. Later, entering AI, he studied TensorFlow's pain points and rebuilt AI infrastructure from scratch. Lattner notes that long-lasting, scalable systems share outstanding architecture and extensibility, driven by a culture of technical excellence.

"Those able to run stably long-term, with strong extensibility and success, rely on excellent architectural design and extreme extensibility. Teams pursue technical perfection together."

Reference: https://www.fast.ai/posts/2025-10-30-build-to-last.html

2. Lalit Maganti: Don't Answer the First Question

Perfetto expert Lalit Maganti observes that the first question asked is often not the real problem. Example: a user asked how to split a Perfetto trace into multiple files. The underlying need was better visualization of long traces, but long traces shouldn't exist at all — Perfetto already supports periodic trace snapshots (short repeated recordings) that eliminate the need for long traces. Maganti uses a mental checklist:

Have I seen this before? If not, slow down.

Does the question sound reasonable? If not, find the normal question underneath.

Does it fit the tool's shape, or is the user fighting the architecture?

He notes users often don't know what they want or understand the problem they're solving. Reference: https://lalitm.com/post/dont-answer-the-first-question/

3. Addy Osmani: Socratic Questioning to Break Analogy Thinking

Addy Osmani advocates Socratic questioning to break analogy thinking and path dependence in software engineering. The process: clarify product goals, challenge assumptions, decompose requirements, and iterate. Core idea: strip away historical inertia, return to problem essence, and focus on true user needs and fundamental constraints (performance, security, etc.). Reference: https://addyosmani.com/blog/first-principles-thinking-software-engineers/

4. Bashi (Muhammed Basith): Bottleneck Classification Pattern

Bashi presents a pattern for system design from first principles: every bottleneck is either a compute, storage, or network problem, each with distinct solutions.

Compute problems (too much processing): add processing capacity, better algorithms, push work to clients, defer with queues.

Storage problems (too much data or reads/writes): caching (reads), read replicas (read scale), sharding (write scale), rethink data model.

Network problems (too much data moving slowly across hops): move data closer (CDNs, edge caching), reduce transfer size (compression), reduce round trips (batching, denormalization).

The hard part is reasoning clearly about constraints and trade-offs under uncertainty. Reference: https://muhammedbasith.medium.com/how-senior-engineers-actually-approach-system-design-from-first-principles-343bd7f41221

5. Sayali Salunke: The Uncomfortable Truth About Microservices

Starting from physical limits of distributed systems, Salunke critiques blind microservice adoption. Microservice complexity manifests as debugging hell, distributed transaction nightmares, and organizational complexity multipliers (Conway's Law). She proposes a decision framework:

What specific bottleneck am I addressing? (Not abstract "scaling")

What's the complexity cost? Have you calculated what you're adding?

Am I solving a technical or organizational problem? If organizational, better ways may exist.

What's my failure mode? What do I lose by splitting? Can I mitigate otherwise?

Is the pain real or hypothetical? Don't split until it hurts; you can always split later.

Reference: https://medium.com/@sayali.sk333/system-design-from-first-principles-the-uncomfortable-truth-about-microservices-f8da9910f590

6. Vikash Gupta: Baby Steps in Middleware Design

Gupta reduces complex middleware and component design to physical essences: storing facts, hard fault-tolerance constraints. His method is top-down, taking baby steps: "No matter what problem, go really small. One tiny step at a time." He illustrates with a short URL generator design process. Reference: https://hiimvikash.medium.com/01-the-first-time-system-design-made-sense-to-me-1d10fd357c99

7. Leon Pennings: Domain Knowledge as First Principle

Pennings argues software architecture decisions must start from domain knowledge, not industry conventions or frameworks. Using a refrigerator design analogy, he criticizes choosing tech stack first then stuffing business logic. First-principles engineering reasons from what must be true:

What problem exists independently of our tools?

What constraints are inherent?

What behavior must be preserved regardless of implementation?

What cannot be simplified away?

Engineering starts with understanding, captured in the domain model — where essential complexity lives, responsibility is clarified, and architecture gains meaning. Reference: https://dev.to/leonpennings/engineering-from-first-principles-why-software-architecture-must-start-with-the-domain-4033

8. Rajeev Sharma: Question Every Abstraction

Sharma's blueprint for innovation: question every abstraction, dependency, and "that's how it's always been done" approach. Reference: https://dev.to/leonpennings/engineering-from-first-principles-why-software-architecture-must-start-with-the-domain-4033

9. Maveneer Team: First Principles Design Definition

Maveneer defines first principles design as starting not with "what's been done" but with "what must be true." Three core questions:

What are the core needs of the user?

What constraints truly exist — and which are assumed?

What does success look like when you remove legacy thinking?

Applied to UX: interrogate every piece — why is this button here? Does the user really want this feature or did we copy it? Is this workflow for convenience or legacy systems? Reference: https://medium.com/@rickyufv/

10. Mohammad Idrees: Designing Systems by Questioning

Idrees provides a concrete questioning framework for system design:

What are the things that exist? (Nouns in the system)

Which change over time ? This introduces state .

Which data is identity vs state ?

What events can happen independently ? Async is about timing , not microservices.

What must never be allowed to happen? These are invariants .

Where can the system safely lose information ?

Reference: https://dev.to/mohammadidrees/designing-systems-by-questioning-from-first-principles-1p6g

Summary

The unifying theme: first principles design demands deep understanding of the problem before any solution. Spend more time on the problem itself — whether it needs solving, what its true nature is, and what constraints are fundamental versus assumed. This approach avoids copying legacy patterns, over-engineering, and solving the wrong problems.