01
4MCP from Zero
Coding agents · About 40 min
How the Model Context Protocol works on the wire, then build a server that gives an agent your own tools and data.
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Courses on one topic each, and papers for the library, all in the same animated format. The most voted get made first.
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Agents in CI with the Agent SDK
Coding agents · About 50 min
Run the agent headless in a pipeline, then build a custom agent on the same engine.
- 032
RAG That Holds Up in Production
AI systems · About 60 min
Chunking, embeddings, hybrid search and reranking, plus the freshness and access-control problems demos skip.
- 042
Evals for LLM Apps
AI systems · About 50 min
Golden sets, regression suites and LLM-as-judge, and how to tell when a judge is lying to you.
- 052
Designing an Agent Runtime
AI systems · About 60 min
Durable execution, idempotent tools, cancellation and sandboxing: the distributed systems inside every agent.
- 062
B-Trees: How Every Database Index Works
Data structures · About 20 min
From a sorted array to the B+ tree under Postgres and SQLite, page by page.
- 072
Bloom Filters and Friends
Data structures · About 25 min
Bloom filters, HyperLogLog and count-min sketch: trading a little accuracy for a lot of memory.
- 082
Dynamic Programming, One Pattern at a Time
Data structures · About 70 min
Memoization to tabulation, then the five DP shapes that cover most problems you will meet.
- 091
Claude Code in an Afternoon
Coding agents · About 60 min
Install it, learn the agent loop, then steer it with plan mode and permission modes on a real repo.
- 101
Context Engineering for Coding Agents
Coding agents · About 30 min
CLAUDE.md, memory, compaction and checkpoints: what the agent sees, and how to keep it sharp in long sessions.
- 111
Skills and Hooks
Coding agents · About 45 min
Turn your repeated prompts into self-loading skills and your rules into hooks the agent cannot skip.
- 121
Subagents and Parallel Work
Coding agents · About 50 min
Worktrees, subagents and background sessions: run several agents on one codebase without them colliding.
- 131
How LLM Inference Works
AI systems · About 45 min
Tokens, the KV cache, prefill versus decode and batching: why your model call costs what it costs.
- 141
Prompt Injection, Attack by Attack
AI systems · About 30 min
Direct, indirect and exfiltration attacks walked through on a real agent, and the defenses that actually help.
- 151
Building with LLM APIs
AI systems · About 50 min
Prompts, structured output, streaming, retries and token budgets, from one API call to a feature you can ship.
- 161
Build an Agent from Scratch
AI systems · About 50 min
Tool calling and the agent loop in plain code, with tools, stop conditions, errors and memory.
- 171
Design an LLM Gateway
AI systems · About 50 min
Routing, fallbacks, caching, rate limits and cost tracking in front of every model call.
- 181
How the Web Works
Backend · About 60 min
Follow one request from a URL to a response through DNS, TCP, TLS, HTTP and the proxies in between.
- 191
API Design That Ages Well
Backend · About 60 min
Resources, errors, pagination, idempotency keys and versioning, on one API that keeps growing.
- 201
Postgres for Application Developers
Backend · About 75 min
Model the data, write the queries, then read a query plan and add the index that fixes it.
- 211
Transactions and Isolation
Backend · About 60 min
What a transaction promises, the anomalies each isolation level allows, and how to stop lost updates.
- 221
Design an Auth System
Backend · About 60 min
Passwords, sessions, cookies, magic links and OAuth, and the attack each piece stops.
- 231
How Containers Work
Backend · About 45 min
Images, layers, namespaces and cgroups, then one service shipped as a container.
- 241
Graph Algorithms for Working Engineers
Data structures · About 35 min
Topological sort, Dijkstra and spanning trees, each tied to a build system, router or network you already use.
- 250
Inside Cursor and Claude Code
AI systems · About 40 min
A teardown of how two coding agents plan, edit and verify, built from their public docs and behavior.
- 260
Design a Top-K Service
System design · About 45 min
Count the best sellers or trending posts across millions of events a second, first exactly and then with a sketch.
- 270
Back-of-the-Envelope Capacity Planning
System design · About 30 min
Estimate servers, storage and bandwidth for a site the size of Reddit with a few numbers you can remember.
- 280
Design a URL Shortener
System design · About 45 min
The classic warm-up, run start to finish the way an interview runs: requirements, estimates, API, data model and deep dives.
- 290
Design a Rate Limiter
System design · About 45 min
Token buckets, sliding windows and a shared counter store, from one server to a whole fleet.
- 300
Design a Cache
System design · About 60 min
Put a cache in front of a slow database, then grow it into a cluster with consistent hashing, eviction and stampede control.
- 310
Design a News Feed
System design · About 60 min
Fan-out on write versus on read, celebrity accounts, ranking and the caches behind a fast timeline.
- 320
Design a Chat App
System design · About 60 min
WebSockets, presence, message ordering, delivery receipts and offline sync for millions of phones.
- 330
Logs, Metrics and Traces
Backend · About 50 min
Instrument one service so you can say what broke, where and since when, without guessing.
- 340
How a Program Runs
Backend · About 60 min
From a binary on disk to a running process: instructions, syscalls, interrupts, scheduling, virtual memory, fork and exec.
- 350
Backtracking, One Template
Data structures · About 40 min
Subsets, permutations and combinations with one recursive template, and how to prune it.
- 360
Greedy Algorithms and Intervals
Data structures · About 40 min
When a greedy choice is provably right, plus merging, scheduling and sweeping intervals.