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Mental Models

The thinking layer under every system you will ever touch.

The universal models that appear in every corner of computing: queues, caches, state machines, trust boundaries. Each one taught with its real math on an interactive chart, then proven hands-on in more than one subsystem, so what you learn in one domain shows up for you in the next. This track makes every other track land faster.

8 hands-on labs across 5 modules, about 3 hours of work. Every lab runs on a real virtual machine in your browser, and checks your work on the machine itself.

Modules and labs

How Experts Actually Think

Before the models: what expertise physically is. Why experience alone plateaus, why skills refuse to transfer between domains, and the one exception this whole track is built on. Grounded in verified research, not folklore.

• The Transfer Rule - Why skills refuse to move between domains (far transfer is rare, chunks are domain-keyed), the one exception the research allows (schema induction across two or
• The Pattern Library in Your Head - What expertise physically is: a library of chunks built by practice at the edge of ability. The scrambled-board result, why experience alone plateaus, and the f

Everything is a Queue

The most universal model in systems. Every latency spike you have ever debugged had a queue behind it: CPU run queues, socket backlogs, disk queues, lock wait lists. Learn the real math (wait time, Little's Law, the 80 percent knee), then read live queues on real machines.

• Everything is a Queue - The most universal model in systems: every latency spike has a queue behind it. The real M/M/1 math on an interactive chart, the 80 percent knee, utilization vs
• Lab: Read the Run Queue - Hands-on instantiation of the queue model on a real machine: measure capacity with nproc, flood the CPU with 8 hogs, watch the 1-minute load climb past the core
• Lab: Read the Accept Queue - The queue model in its second subsystem: find a socket's accept queue with ss, fill it to its backlog, watch the kernel silently ignore the overflow, then wake

The Latency Hierarchy

Nine orders of magnitude separate a memory read from a cross-continent packet, and every performance decision you will ever make lives somewhere on that ladder. Learn the rungs, then measure them yourself on a real machine: RAM vs disk vs network, predicted first, measured second.

• The Latency Hierarchy - The ladder of latency: operations differ by powers of ten, not percentages. Measure loopback vs the internet (34,000x apart), fall into a virtualization trap on

Caching and Invalidation

Keep a copy of recent answers closer and most work disappears, but every cached answer might be a lie. The hit-ratio math (why 99 percent is a different world from 90), the page cache made visible on a real machine, and the invalidation bargain every cache signs.

• Caching and Invalidation - The third universal model: keep a copy closer, pay in staleness. Why 99 percent hits beats 90 by 5.5x (played on a live chart), the page cache caught red-handed

State Machines

Systems do not drift, they jump between named states along drawn edges. Read live TCP socket states with ss (including the famous forgotten-close leak), watch process states flip under signals, and learn the first question of every incident: what state is it in, and what transition is it waiting for?

• State Machines - The fourth universal model: named states, events, allowed transitions. Read live TCP states through a full lifecycle (including the CLOSE-WAIT leak that weekly

Frequently asked questions

How many labs are in Mental Models?

Mental Models has 8 hands-on labs, roughly 3 hours of guided work, spread across 5 modules.

Do I need my own server or hardware to do the Mental Models labs?

No. Every lab boots a real virtual machine in your browser, with a real Linux shell. There is nothing to install, and nothing on your own machine to break.

What level is Mental Models?

Labs in this track are rated beginner. The track starts from the beginning, so no prior experience is assumed.