The whole curriculum, free

8 tracks and 41 modules, in the order they build on each other. Every module ends in a drill you have to actually beat, and every one of them is free — there is no paid tier of the material.
How the Network Actually Works
5 hours
6 lessons
Beginner
How the Network Actually Works
Free
01.1
Latency Numbers & Estimation
4 hours
5 lessons
Beginner
Latency Numbers & Estimation
Free
01.2
The Machine Underneath
5 hours
5 lessons
Beginner
The Machine Underneath
Free
01.3
Consistency, Availability & Partitions
5 hours
5 lessons
Beginner
Consistency, Availability & Partitions
Free
01.4
API Design & Contracts
4 hours
5 lessons
Beginner
API Design & Contracts
Free
01.5
Relational Modelling
5 hours
5 lessons
Beginner
Relational Modelling
Free
02.1
Indexes & Query Plans
5 hours
5 lessons
Beginner
Indexes & Query Plans
Free
02.2
Transactions & Isolation
5 hours
5 lessons
Beginner
Transactions & Isolation
Free
02.3
NoSQL & Choosing a Data Model
5 hours
6 lessons
Beginner
NoSQL & Choosing a Data Model
Free
02.4
Replication
5 hours
5 lessons
Beginner
Replication
Free
02.5
Partitioning & Sharding
5 hours
5 lessons
Beginner
Partitioning & Sharding
Free
02.6
Cache Strategies & Invalidation
4 hours
5 lessons
Intermediate
Cache Strategies & Invalidation
Free
03.1
Distributed Caches
4 hours
5 lessons
Intermediate
Distributed Caches
Free
03.2
CDNs & the Edge
4 hours
5 lessons
Intermediate
CDNs & the Edge
Free
03.3
Object Storage & Media
4 hours
5 lessons
Intermediate
Object Storage & Media
Free
03.4
Queues & Background Workers
4 hours
5 lessons
Intermediate
Queues & Background Workers
Free
04.1
Publish/Subscribe
4 hours
5 lessons
Intermediate
Publish/Subscribe
Free
04.2
Log-Based Streaming
5 hours
5 lessons
Intermediate
Log-Based Streaming
Free
04.3
Delivery Semantics & Idempotency
4 hours
5 lessons
Intermediate
Delivery Semantics & Idempotency
Free
04.4
Event-Driven Architecture
4 hours
5 lessons
Intermediate
Event-Driven Architecture
Free
04.5
Load Balancing
4 hours
5 lessons
Intermediate
Load Balancing
Free
05.1
Consistent Hashing
3 hours
5 lessons
Intermediate
Consistent Hashing
Free
05.2
Rate Limiting & Quotas
3 hours
5 lessons
Intermediate
Rate Limiting & Quotas
Free
05.3
Stateless Services & Session State
3 hours
5 lessons
Intermediate
Stateless Services & Session State
Free
05.4
Search & Indexing at Scale
4 hours
5 lessons
Intermediate
Search & Indexing at Scale
Free
05.5
Failure Modes & Blast Radius
4 hours
5 lessons
Advanced
Failure Modes & Blast Radius
Free
06.1
SLOs & Error Budgets
3 hours
5 lessons
Advanced
SLOs & Error Budgets
Free
06.2
Observability
4 hours
5 lessons
Advanced
Observability
Free
06.3
Timeouts, Retries & Circuit Breakers
3 hours
5 lessons
Advanced
Timeouts, Retries & Circuit Breakers
Free
06.4
Deployment, Migration & Rollback
4 hours
5 lessons
Advanced
Deployment, Migration & Rollback
Free
06.5
Design a URL Shortener
3 hours
5 lessons
Advanced
Design a URL Shortener
Free
07.1
Design a News Feed
4 hours
5 lessons
Advanced
Design a News Feed
Free
07.2
Design a Chat System
4 hours
5 lessons
Advanced
Design a Chat System
Free
07.3
Design a Rate-Limited Public API
3 hours
5 lessons
Advanced
Design a Rate-Limited Public API
Free
07.4
Design a Video Platform
4 hours
5 lessons
Advanced
Design a Video Platform
Free
07.5
Design a Payment System
4 hours
5 lessons
Advanced
Design a Payment System
Free
07.6
The Forty-Five Minutes
2 hours
4 lessons
All levels
The Forty-Five Minutes
Free
08.1
Requirements & Scoping
2 hours
4 lessons
All levels
Requirements & Scoping
Free
08.2
Drawing the Diagram
2 hours
4 lessons
All levels
Drawing the Diagram
Free
08.3
Deep Dives & Defending Trade-offs
3 hours
5 lessons
All levels
Deep Dives & Defending Trade-offs
Free
08.4
Behavioral Rounds & Negotiation
3 hours
5 lessons
All levels
Behavioral Rounds & Negotiation
Free
08.5
How the Network Actually Works
5 hours
6 lessons
Beginner
How the Network Actually Works
Free
01.1
Latency Numbers & Estimation
4 hours
5 lessons
Beginner
Latency Numbers & Estimation
Free
01.2
The Machine Underneath
5 hours
5 lessons
Beginner
The Machine Underneath
Free
01.3
Consistency, Availability & Partitions
5 hours
5 lessons
Beginner
Consistency, Availability & Partitions
Free
01.4
API Design & Contracts
4 hours
5 lessons
Beginner
API Design & Contracts
Free
01.5
Relational Modelling
5 hours
5 lessons
Beginner
Relational Modelling
Free
02.1
Indexes & Query Plans
5 hours
5 lessons
Beginner
Indexes & Query Plans
Free
02.2
Transactions & Isolation
5 hours
5 lessons
Beginner
Transactions & Isolation
Free
02.3
NoSQL & Choosing a Data Model
5 hours
6 lessons
Beginner
NoSQL & Choosing a Data Model
Free
02.4
Replication
5 hours
5 lessons
Beginner
Replication
Free
02.5
Partitioning & Sharding
5 hours
5 lessons
Beginner
Partitioning & Sharding
Free
02.6
Cache Strategies & Invalidation
4 hours
5 lessons
Intermediate
Cache Strategies & Invalidation
Free
03.1
Distributed Caches
4 hours
5 lessons
Intermediate
Distributed Caches
Free
03.2
CDNs & the Edge
4 hours
5 lessons
Intermediate
CDNs & the Edge
Free
03.3
Object Storage & Media
4 hours
5 lessons
Intermediate
Object Storage & Media
Free
03.4
Queues & Background Workers
4 hours
5 lessons
Intermediate
Queues & Background Workers
Free
04.1
Publish/Subscribe
4 hours
5 lessons
Intermediate
Publish/Subscribe
Free
04.2
Log-Based Streaming
5 hours
5 lessons
Intermediate
Log-Based Streaming
Free
04.3
Delivery Semantics & Idempotency
4 hours
5 lessons
Intermediate
Delivery Semantics & Idempotency
Free
04.4
Event-Driven Architecture
4 hours
5 lessons
Intermediate
Event-Driven Architecture
Free
04.5
Load Balancing
4 hours
5 lessons
Intermediate
Load Balancing
Free
05.1
Consistent Hashing
3 hours
5 lessons
Intermediate
Consistent Hashing
Free
05.2
Rate Limiting & Quotas
3 hours
5 lessons
Intermediate
Rate Limiting & Quotas
Free
05.3
Stateless Services & Session State
3 hours
5 lessons
Intermediate
Stateless Services & Session State
Free
05.4
Search & Indexing at Scale
4 hours
5 lessons
Intermediate
Search & Indexing at Scale
Free
05.5
Failure Modes & Blast Radius
4 hours
5 lessons
Advanced
Failure Modes & Blast Radius
Free
06.1
SLOs & Error Budgets
3 hours
5 lessons
Advanced
SLOs & Error Budgets
Free
06.2
Observability
4 hours
5 lessons
Advanced
Observability
Free
06.3
Timeouts, Retries & Circuit Breakers
3 hours
5 lessons
Advanced
Timeouts, Retries & Circuit Breakers
Free
06.4
Deployment, Migration & Rollback
4 hours
5 lessons
Advanced
Deployment, Migration & Rollback
Free
06.5
Design a URL Shortener
3 hours
5 lessons
Advanced
Design a URL Shortener
Free
07.1
Design a News Feed
4 hours
5 lessons
Advanced
Design a News Feed
Free
07.2
Design a Chat System
4 hours
5 lessons
Advanced
Design a Chat System
Free
07.3
Design a Rate-Limited Public API
3 hours
5 lessons
Advanced
Design a Rate-Limited Public API
Free
07.4
Design a Video Platform
4 hours
5 lessons
Advanced
Design a Video Platform
Free
07.5
Design a Payment System
4 hours
5 lessons
Advanced
Design a Payment System
Free
07.6
The Forty-Five Minutes
2 hours
4 lessons
All levels
The Forty-Five Minutes
Free
08.1
Requirements & Scoping
2 hours
4 lessons
All levels
Requirements & Scoping
Free
08.2
Drawing the Diagram
2 hours
4 lessons
All levels
Drawing the Diagram
Free
08.3
Deep Dives & Defending Trade-offs
3 hours
5 lessons
All levels
Deep Dives & Defending Trade-offs
Free
08.4
Behavioral Rounds & Negotiation
3 hours
5 lessons
All levels
Behavioral Rounds & Negotiation
Free
08.5
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Systems worked end to end

Frequently asked questions

Is the curriculum really free?
Who is this for?
Is any of it available yet?
Why are there no testimonials or success stories?
Does the application assistant apply to jobs for me?
What does Pro cost?

Start at track one. It assumes nothing.