AI writes the code.
You design the system.

fivenines is a structured mastery platform for software engineers who want to actually understand what's happening underneath — from memory hierarchy to multi-datacenter consensus. Not passive content. Real practice, real feedback, real progress.

130+ concepts · 100 design problems · AI-scored architecture reviews

architecture_simulation.run
live
💻
Client
GET /api/feed
🌐
CDN
CloudFront
⚖️
Load Balancer
Round-robin
⚙️
API Server
Node.js × 1
Cache
Redis
🗄️
Database
Single primary
✓ Cache hit
Static assets served from edge. 12ms. No origin hit needed.
⚠ No health checks
Round-robin routes to unhealthy instances. Add active probes.
⚠ Cache miss — 100%
No TTL set on feed keys. Every request hits the DB cold.
✕ Write contention
Single primary at 94% capacity. No read replicas. Failure point.
Latency
Fault Tol.
Scalability
Consistency
Cost
The quiet shift

Every junior to mid-level engineer is watching their role description get absorbed into a prompt. The ones who survive that compression are the ones who move up fast enough to do the work AI can't do.

AI is commoditizing the layer that was already commodity work — boilerplate, CRUD, syntax — while dramatically raising the premium on engineers who understand what's happening underneath.

When Copilot generates code, someone still has to decide whether the architecture will hold up at 10 million users, survive a network partition, or avoid a thundering herd. That judgment can't be prompted into existence. fivenines trains exactly that judgment.

The market for senior engineers doing architecture work is expanding. AI makes it faster to build things, so more things are being built. The demand for people who can design them correctly doesn't shrink — it grows.

The map

130+ concepts. One dependency graph.

Most platforms hand you a list of topics and say “good luck.” fivenines organizes everything as a directed acyclic graph — a DAG — where every concept explicitly depends on the ones that come before it.

Hardware Layer
TransistorsCPU CacheMemory Hierarchy
↓ depends on
OS Layer
ProcessesVirtual MemoryFile Systems
↓ depends on
Networking Layer
TCP/IPDNSLoad Balancing
↓ depends on
Distributed Systems
ReplicationConsensusSharding

See the full picture

The graph shows the entire landscape — all four domains, all the connections. You always know where you are, what's ahead, and why it matters.

Learn what's relevant to you

Pick your target — say, distributed consensus — and the graph highlights exactly the prerequisite path. No guessing, no gaps, no wasted time on things you don't need yet.

Never learn something you're not ready for

Dependencies are enforced. You always have the foundations. That's why concepts click instead of confuse.

Concise, high-signal tutorials

Every concept is a focused article — not a 40-minute video. Clear SVG diagrams, real-world use cases, worked examples, and Q&A sections for maximum retention.

The feedback

Draw your system. Hit Deploy.
AI simulates what happens next.

Design an architecture in the Mermaid editor and click Deploy. Our AI simulates a production deployment against your specific diagram — then writes you a scored postmortem. Not generic suggestions. Feedback tied to your design.

Degraded
URL Shortener — Postmortem
Simulated · 10,000 rps · 3 regions · 48hr window
Scalability
7.2
Fault Tol.
4.8
Consistency
8.1
Latency
6.5
Cost
3.2
Critical — Write Path Bottleneck

Your single Redis instance becomes the bottleneck above 8,000 ops/sec. At simulated peak (10k rps), write latency degrades to 340ms with 12% error rate. Fix: Add write-behind caching with partitioned shards.

Warning — No Failover Path

Region us-east-1 failure takes down all write operations. Consider active-passive replication with automated failover.

Pass — Read Path

CDN + cache layer handles read traffic well. p99 read latency holds at 18ms across all simulated regions.

Not “consider caching”

The AI finds the exact bottleneck in your design and the threshold where it breaks. That's the difference between generic advice and real architectural feedback.

A learning artifact you keep

Every postmortem is a document you can return to — compare across iterations, track how your designs improve, build evidence of actual skill development.

The loop

Read. Code. Design. Ship.

Every concept tutorial is a complete learning loop — not just reading, but doing. Each one follows the same structure so you build real retention, not just familiarity.

01

Learn the theory

Concise, high-signal articles with SVG diagrams, real-world use cases, and worked examples. No fluff, no 40-minute videos. Read it, understand it, move on.

02

Test your understanding

Quizzes and Q&A sections that catch the gaps you didn't know you had. Targeted checks on the parts that actually trip people up.

03

Write the code

Live coding challenges in a Monaco editor, executed and verified via Judge0. Real test cases, real execution. Your code either passes or it doesn't.

04

Design & deploy

Draw your architecture in the Mermaid editor, hit deploy, get a scored postmortem. Iterate until it's operational.

The community

One problem, a hundred architectures.

Every design problem can be solved a dozen different ways. The fastest way to grow as an architect is to see how engineers more experienced than you approached the same problem — what tradeoffs they chose, what you missed, what you'd never have considered.

@kiran.devSenior
URL Shortener — Event-Sourced
CQRS with event sourcing, separate read/write stores, eventual consistency via Kafka
★★★★★ 4.9 · 127 votes
@maya.systemsStaff
URL Shortener — Cell-Based
Cell-based architecture with regional failover, DynamoDB global tables, edge caching
★★★★★ 4.8 · 94 votes
@alex.archMid
URL Shortener — Simple & Solid
Postgres + Redis + Nginx. No frills. Handles 50k rps with proper indexing and connection pooling
★★★★☆ 4.3 · 210 votes

100 design problems mapped across career levels from Junior to Senior Staff. A leaderboard and rating system so the best solutions rise to the top. This is how you grow exponentially faster than reading blog posts alone.

The signal

XP is earned, not given.

Every other platform gives you credit for watching a video. fivenines gives you XP only when your code passes test cases and your design survives deployment. The leaderboard badge isn't self-reported — it's verified.

Everyone else

  • Watched video → +50 XP
  • Read chapter → +30 XP
  • Clicked “Mark complete” → +20 XP
  • Progress = consumption

fivenines

  • Code passes all test cases → +XP
  • Design scores operational → +XP
  • Database verifies execution
  • Progress = proven ability
The alternative

You know what it's like without this.

ByteByteGo chaptersRandom blog postsDDIA bookYouTube talksExponent
None of them talk to each other. No feedback loop. No structure. No way to know what to learn next.
fivenines is the one place where the curriculum is a graph that enforces order, the coding is real, the designs are scored, and the community shows you every way a problem can be solved.
How it compares
Concept GraphLive CodingAI EvaluationCommunity DesignsCareer Levels
LeetCode / NeetCode
ByteByteGo / Educative
Coursera / MIT OCW
fivenines
The math

Let's talk ROI.

$18
Per month
$50k–200k
Salary delta per level-up

One passed system design round at a mid-tier tech company is worth $50k–$200k in salary delta. One round pays for 8 years of Pro.

Plans

Start free. Upgrade when it clicks.

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  • Explore the full concept graph
  • 20 tutorials with XP
  • 10 design problems
  • 5 AI deploy simulations/mo
  • Browse community solutions
  • Publish solutions
  • Full 100-problem curriculum
  • Unlimited AI deploys
Get started free
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per year · just $12/mo
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99.999% availability.
That's the standard.

The aspiration isn't to learn about distributed systems. It's to think and build like someone who ships them.

Dependency-aware curriculum · AI-scored designs · Real coding challenges · Community solutions