# Ratstack Tube

> For agents: start with the [agent guide](https://ratstack.sh/llms.txt). Every page is Markdown by default; add `Accept: text/html` for HTML.

Videos worth your time if you are learning this stack, most of them by the people who build the tools. Each one comes with a short take on what you learn from it.

Tiers run from S to F by how useful the video is to someone learning this stack. Within a tier, order is editorial. Titles, channels, durations and dates come from YouTube. Each entry shows the date we checked it and what its take was checked against.

Thumbnails load from YouTube's image host. A video plays from youtube-nocookie.com only after you press its play button. Every title links to the video on youtube.com.

## Effect

Typed failures, services and layers, structured concurrency, Schema, and where Effect is heading.

- **S tier**: [Production-Grade TypeScript by Johannes Schickling (Effect Days 2024)](https://www.youtube.com/watch?v=PxIBWjiv3og) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 26:57, published 2024-03-26, checked 2026-11-08 against the transcript. The opening keynote of Effect Days 2024 makes the case for Effect: production TypeScript has to handle errors, retries, timeouts and observability, and Effect gives you one set of primitives for all of them. Start here to learn why the stack is built on it.
- **S tier**: [Effect TypeScript Library: Beginner / Intermediate Workshop (Effect Days 2024)](https://www.youtube.com/watch?v=Lz2J1NBnHK4) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 4:16:31, published 2024-04-26, checked 2026-11-08 against the transcript. Ethan Niser's four-hour workshop goes from what an Effect is to running effects, error handling, context, resources, Schema and fibers, with the workshop code in a public repo. Work through it once and the rest of this list gets easier.
- **S tier**: [Production-grade app architecture with Effect (Workshop Part 1 – Effect Days 2025 )](https://www.youtube.com/watch?v=upXJJ9maWPc) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 2:40:20, published 2025-04-29, checked 2026-11-08 against the transcript. Maxwell Brown builds an app out of services, then provides them with layers, including layers that own resources and layers that depend on other layers. It is the clearest walk through the service-and-layer shape this stack uses everywhere.
- **S tier**: [Stop agent slop with Effect |  Mattia Manzati | Effect Milan 2026 🇮🇹](https://www.youtube.com/watch?v=88XERFAibQc) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 33:52, published 2026-06-25, checked 2026-11-08 against the transcript. Mattia Manzati shows how to keep agent-written code honest with Effect: the Effect LSP turns a missing requirement into a plain diagnostic where the compiler only reports an assignability error, then lint rules, tests, and watching the code run. It is the same kind of fence this stack runs.
- **A tier**: [Building Effect 4.0 | Michael Arnaldi (Effect Days 2025)](https://www.youtube.com/watch?v=nyvB6nRe5x0) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 42:35, published 2025-04-08, checked 2026-11-08 against the transcript. Michael Arnaldi walks through what changed in Effect 4.0: smaller bundles, a simpler runtime, the new queue API, STM in core and simpler Layer APIs. Watch it to understand the version this stack pins.
- **A tier**: [The Simple Secret Behind Effect’s Power](https://www.youtube.com/watch?v=F5aWLtEdNjE) by [Kit Langton](https://www.youtube.com/@kitlangton), 17:53, published 2025-08-05, checked 2026-11-08 against the description. Kit Langton rebuilds the core idea of an effect system from thunks, then adds repeat, retry, timing and a generator syntax on top. You learn why describing work as a value is what makes those combinators possible.
- **A tier**: [Effect: the unreadable library that captured my heart](https://www.youtube.com/watch?v=S2GChOwivwQ) by [Matt Pocock](https://www.youtube.com/@mattpocockuk), 13:03, published 2025-06-29, checked 2026-11-08 against the transcript. Matt Pocock gives a fast tour of Effect's syntax, typed errors and dependency injection, and why he came round to it. A good first look if you have thirteen minutes.
- **A tier**: [Effect Schema V4 Crash Course](https://www.youtube.com/watch?v=0naAPm0-0Wg) by [Lucas Barake](https://www.youtube.com/@lucas-barake), 36:01, published 2026-06-29, checked 2026-11-08 against the description. Lucas Barake covers Effect Schema v4 from a basic struct to transformations, discriminated unions, normalizing API data and a real boundary example. Schemas are the contract in this stack, so this is required reading in video form.
- **A tier**: [Structured Concurrency: The hidden power behind Effect | Antoine Coulon (Effect Days 2025)](https://www.youtube.com/watch?v=do5KCcCgS18) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 10:56, published 2025-05-20, checked 2026-11-08 against the transcript. Antoine Coulon explains structured concurrency and how Effect's fibers and scopes keep the relationships between concurrent tasks, so interruption and cleanup work. Ten minutes on the concurrency model under every Effect program.
- **B tier**: [Effectifying OpenCode // Kit Langton // Cause & Effect 8](https://www.youtube.com/watch?v=-mL7VVvkLGM) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 1:45:31, published 2026-06-19, checked 2026-11-08 against the transcript. Kit Langton talks with Johannes Schickling about bringing Effect into OpenCode: Schema and branded IDs, services and layers, testing LLM workflows, and incremental adoption in a large TypeScript codebase. Watch it to see a real migration rather than a demo.
- **B tier**: [Next-gen DevTools for Effect | Mattia Manzati (Effect Days 2025)](https://www.youtube.com/watch?v=ZCHNLS8e0os) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 15:41, published 2025-06-13, checked 2026-11-08 against the transcript. Mattia Manzati tours Effect's developer tooling, including the language service plugin. This stack turns those language service diagnostics into build failures, so it helps to know where they come from.
- **B tier**: [Effect Schema v4, Effectful Schemas, Schema Representations](https://www.youtube.com/watch?v=wFNbDkE69_U) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 14:13, published 2026-03-13, checked 2026-11-08 against the transcript. A short clip on what changed in Schema v4, effectful schemas, and schema representations. Useful after the crash course above.
- **B tier**: [Effect Cluster | Tim Smart (Effect Days 2025)](https://www.youtube.com/watch?v=4lEDdMuTDJg) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 24:43, published 2025-05-13, checked 2026-11-08 against the transcript. Tim Smart introduces Effect Cluster, built on Effect RPC, where runners own shards of entities and persistence lives in the messaging layer. Durable workflows build on top of it, so learn the vocabulary before you need durable execution.
- **B tier**: [Cluster, Workflows & Cloudflare Durable Objects](https://www.youtube.com/watch?v=CBPttaqp9Ec) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 31:23, published 2026-10-12, checked 2026-11-08 against the transcript. An office-hours segment that untangles how Effect Cluster, Effect Workflows and Cloudflare Durable Objects relate: cluster as an actor framework of sharded entities, and workflows that run on a workflow engine layer, which today means the cluster engine or an in-memory one.
- **C tier**: [Effect on the Frontend: When, Why, How | Sandro Maglione (Effect Days 2025)](https://www.youtube.com/watch?v=G_jp87gxILE) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 12:42, published 2025-05-23, checked 2026-11-08 against the transcript. Sandro Maglione covers when Effect earns its place in front-end code, how he sets a project up, and a worked example with separate client and server runtimes. Watch it if you are deciding how far Effect should reach into the browser.
- **C tier**: [Effect for Beginners](https://www.youtube.com/watch?v=fTN8BX5qj6s) by [Ethan Niser](https://www.youtube.com/@ethanniser), 28:15, published 2023-08-07, checked 2026-11-08 against the transcript. Ethan Niser's 2023 beginner video covers the Effect type, creating and running effects, pipelines, generators and error handling. The ideas hold, but the APIs predate Effect 4, so prefer the workshop above.

## Alchemy and infrastructure as code

Infrastructure as Effects: cloud resources declared in the same TypeScript program as the code that uses them.

- **S tier**: [Alchemy, Infrastructure as Effects | Office Hours 27 🔥](https://www.youtube.com/watch?v=fPSxB7ZgSJw) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 1:16:00, published 2026-04-29, checked 2026-11-08 against the transcript. Sam Goodwin builds a stack from zero with Alchemy and Effect: runtime code next to infrastructure, Durable Objects and WebSockets, testing, Alchemy against Terraform, and decoupling infrastructure with layers. The best single video on infrastructure as Effects.
- **A tier**: [What is Alchemy? Zero-to-Production Infrastructure in TypeScript & Effect | Office Hours 27](https://www.youtube.com/watch?v=EMbztKSI3-o) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 9:00, published 2026-05-04, checked 2026-11-08 against the transcript. The first nine minutes of that office hours on their own: what Alchemy is, how v2 moved from async TypeScript to Effect, and a demo where state lives in a Durable Object and swaps for local or in-memory state through layers.
- **A tier**: [Alchemy vs Terraform + Decoupling Infrastructure with Layers](https://www.youtube.com/watch?v=83BsUCw3wew) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 12:04, published 2026-06-05, checked 2026-11-08 against the transcript. Sam Goodwin on replacing Terraform with resources written in TypeScript and Effect, and why he keeps a plan you can audit and check before deploying rather than a pure reconciler. Then layers swap D1 for DynamoDB behind one Effect service.
- **B tier**: [Using Skills, Layers, and managing Stages | Sam Goodwin, Founder of Alchemy](https://www.youtube.com/watch?v=_QVf4d1WsAQ) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 10:00, published 2026-06-12, checked 2026-11-08 against the transcript. Sam Goodwin explains the bind-then-use pattern, where declaring a resource dependency also grants only the permissions it needs, and how layers keep heavy provider code out of the runtime bundle.
- **C tier**: [Sam Goodwin - Alchemy](https://www.youtube.com/watch?v=MtKHzAH6uXM) by [devtools-fm](https://www.youtube.com/@devtoolsfm), 49:54, published 2026-05-10, checked 2026-11-08 against the transcript. A podcast with Sam Goodwin on Alchemy v2, his background building cloud tools, the Distilled SDKs, and why he calls it infrastructure as effects. Background listening once you have seen the demos.

## XState and state machines

Finite states, statecharts and actors for lifecycles you can see.

- **S tier**: [Effective State Machines with XState | David Khourshid | Effect Miami 2](https://www.youtube.com/watch?v=m-dSS55VO3Y) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 29:40, published 2026-07-26, checked 2026-11-08 against the transcript. David Khourshid shows how async/await hides errors and flow, models a video player as a state machine in XState, and ends on Effect and XState as complementary tools. It is the pairing this stack uses for lifecycles.
- **A tier**: [Effective state machines for complex logic by David Khourshid (Effect Days 2024)](https://www.youtube.com/watch?v=mZJxGgI7FXU) by [Effect | TypeScript for the AI Era](https://www.youtube.com/@effect-ts), 30:05, published 2024-05-14, checked 2026-11-08 against the transcript. David Khourshid on where state machines sit above Effect for workflows, the difference between actions that fire and forget and actors that are live entities, and the actor model he would like to see in Effect. Pairs with the talk above and goes deeper on actors.
- **A tier**: [David Khourshid: Simplifying Complex UIs with Finite Automata & Statecharts | JSConf Iceland 2018](https://www.youtube.com/watch?v=RqTxtOXcv8Y) by [JSConf](https://www.youtube.com/@jsconf_), 34:28, published 2018-04-05, checked 2026-11-08 against the description. The classic introduction to finite state machines and statecharts for UI: how they tame the growth of possible states, and how to implement, test and visualize them.
- **B tier**: [Webinar: State Machines and Actors with XState v5](https://www.youtube.com/watch?v=1NsSHkao-q4) by [Stately](https://www.youtube.com/@Statelyai), 2:42:16, published 2024-05-03, checked 2026-11-08 against the description. A long Stately webinar that builds a real app with XState v5: actors and machines, inspecting and visualizing logic, framework integration and TypeScript tips. This stack pins an XState 6 beta, so treat the API details as v5.

## TypeScript

The language, its type system, and the native compiler in TypeScript 7.

- **A tier**: [TypeScript 7 Is Here (And It's 10× Faster)](https://www.youtube.com/watch?v=OytpXXeNmTQ) by [Microsoft Developer](https://www.youtube.com/@MicrosoftDeveloper), 10:39, published 2026-07-24, checked 2026-11-08 against the transcript. Anders Hejlsberg introduces TypeScript 7, the Go port of the compiler, with a live compile of the VS Code codebase and the new LSP language server. This stack pins TypeScript 7, so this is the compiler you are running.
- **A tier**: [A 10x Faster TypeScript with Anders Hejlsberg | BRK116](https://www.youtube.com/watch?v=UJfF3-13aFo) by [Microsoft Developer](https://www.youtube.com/@MicrosoftDeveloper), 54:27, published 2025-05-23, checked 2026-11-08 against the description. The longer Build talk on the native port: why the team committed to it, why Go, how it changes your workflow, and the path to completion.
- **B tier**: [GopherCon 2025: Porting the TypeScript Compiler to Go for a 10x Speedup V2 - Jake Bailey](https://www.youtube.com/watch?v=PZm_YbE3fcA) by [Gopher Academy](https://www.youtube.com/@GopherAcademy), 39:17, published 2026-01-06, checked 2026-11-08 against the description. Jake Bailey on porting the 150,000-line compiler and its 90,000 tests to Go, the problems they hit and the lessons they learned. Watch it for the engineering story behind the speedup.
- **B tier**: [Generics: The most intimidating TypeScript feature](https://www.youtube.com/watch?v=dLPgQRbVquo) by [Matt Pocock](https://www.youtube.com/@mattpocockuk), 18:19, published 2023-01-12, checked 2026-11-08 against the transcript. Matt Pocock explains generics from the type level up: passing type arguments, inference, and constraints. Effect's types lean on generics heavily, so this pays off quickly.

## Agents and MCP

How agents work, why tools and skills matter, and where MCP and code mode fit.

- **S tier**: [Code Mode: Let the Code do the Talking - Sunil Pai, Cloudflare](https://www.youtube.com/watch?v=8txf05vVVl4) by [AI Engineer](https://www.youtube.com/@aiDotEngineer), 19:40, published 2026-04-19, checked 2026-11-08 against the transcript. Sunil Pai explains code mode, where the model writes code against an API instead of making JSON tool calls, and why that scales better, with sandboxing and capability-based security. This stack ships a code mode surface, and this is the idea behind it.
- **A tier**: [How We Build Effective Agents: Barry Zhang, Anthropic](https://www.youtube.com/watch?v=D7_ipDqhtwk) by [AI Engineer](https://www.youtube.com/@aiDotEngineer), 15:09, published 2025-04-04, checked 2026-11-08 against the transcript. Barry Zhang on three ideas from Anthropic's Building Effective Agents: don't build agents for everything, keep them simple, and think like your agent. Fifteen minutes that will change how you design tools.
- **A tier**: [The Future of MCP — David Soria Parra, Anthropic](https://www.youtube.com/watch?v=v3Fr2JR47KA) by [AI Engineer](https://www.youtube.com/@aiDotEngineer), 18:45, published 2026-04-19, checked 2026-11-08 against the transcript. David Soria Parra lays out where MCP is going: skills, MCP and computer use as one stack, progressive discovery, programmatic tool calling, and advice for server authors.
- **A tier**: [Don't Build Agents, Build Skills Instead – Barry Zhang & Mahesh Murag, Anthropic](https://www.youtube.com/watch?v=CEvIs9y1uog) by [AI Engineer](https://www.youtube.com/@aiDotEngineer), 16:22, published 2025-12-08, checked 2026-11-08 against the transcript. Barry Zhang and Mahesh Murag argue that agents need packaged expertise more than new scaffolding, and explain Skills as a minimal format for procedural knowledge an agent loads when it needs it.
- **A tier**: [Simon Willison: Engineering practices that make coding agents work - The Pragmatic Summit](https://www.youtube.com/watch?v=owmJyKVu5f8) by [The Pragmatic Engineer](https://www.youtube.com/@pragmaticengineer), 28:20, published 2026-03-19, checked 2026-11-08 against the transcript. Simon Willison on the engineering practices that make coding agents work: tests as the core reliability tool, prompt injection and security, and getting more from current models.
- **B tier**: [Tips for building AI agents](https://www.youtube.com/watch?v=LP5OCa20Zpg) by [Anthropic](https://www.youtube.com/@anthropic-ai), 18:19, published 2025-02-13, checked 2026-11-08 against the transcript. Anthropic's applied AI and research people define agents against workflows, look at the anatomy of an agent prompt, and give advice on where agents help and where they don't.
- **B tier**: [Code Mode: Giving AI Agents an Entire API in 1,000 Tokens (With Demos)](https://www.youtube.com/watch?v=-ZikRWR1Gb4) by [Cloudflare](https://www.youtube.com/@cloudflare), 42:27, published 2026-02-26, checked 2026-11-08 against the transcript. This Week in NET on code mode, with demos: more than 2,500 Cloudflare API endpoints behind two tools and about a thousand tokens of context.
- **C tier**: [Andrej Karpathy: Software Is Changing (Again)](https://www.youtube.com/watch?v=LCEmiRjPEtQ) by [Y Combinator](https://www.youtube.com/@ycombinator), 39:31, published 2025-06-18, checked 2026-11-08 against the description. Andrej Karpathy's talk on Software 3.0: programming in English, LLMs as a new kind of operating system, and designing apps with partial autonomy. Big-picture context rather than technique.

## Cloudflare

Workers, Durable Objects, Queues and Workflows, where this stack runs.

- **S tier**: [Durable Objects Finally Make Sense](https://www.youtube.com/watch?v=k4UXEfZf3sc) by [Cloudflare Developers](https://www.youtube.com/@CloudflareDevelopers), 9:28, published 2026-04-28, checked 2026-11-08 against the transcript. Durable Objects explained by building a Slack-style chat: SQLite state, WebSocket broadcast and hibernation in under seventy lines, and why that makes them stateful serverless functions rather than just storage. Watch it before reading any Durable Object code.
- **A tier**: [Cloudflare Workers Explained](https://www.youtube.com/watch?v=WDhruDqb5nM) by [Cloudflare Developers](https://www.youtube.com/@CloudflareDevelopers), 5:22, published 2026-06-23, checked 2026-11-08 against the transcript. Five minutes on what a Worker is: V8 isolates instead of containers, scaling to zero on Cloudflare's global network, and converting an Express app to a Worker with Hono.
- **A tier**: [How Durable Objects and D1 Work: A Deep Dive with Cloudflare’s Josh Howard](https://www.youtube.com/watch?v=C5-741uQPVU) by [Aaron Francis](https://www.youtube.com/@aarondfrancis), 59:33, published 2025-05-14, checked 2026-11-08 against the transcript. Josh Howard from Cloudflare explains how Durable Objects and D1 work under the hood: isolates, replicated storage, and routing every request for an object to one place. The deep dive once the basics click.
- **B tier**: [Why modern software engineering needs Durable Objects (Cloudflare Connect 2026)](https://www.youtube.com/watch?v=75jxhU6z3ho) by [Cloudflare Developers](https://www.youtube.com/@CloudflareDevelopers), 27:59, published 2026-10-24, checked 2026-11-08 against the description. Ashley Peacock from the Durable Objects team on building resilient long-running agents on stateful infrastructure: platform retries and failure recovery, graceful deploys that protect running state, and lifecycle management.
- **B tier**: [Cloudflare Workflows: The Newest Developer Platform Primitive at Cloudflare](https://www.youtube.com/watch?v=slS4RBV0SBk) by [Cloudflare Developers](https://www.youtube.com/@CloudflareDevelopers), 7:35, published 2024-10-24, checked 2026-11-08 against the transcript. An introduction to Cloudflare Workflows: durable execution that runs in the background in steps, with built-in retries and the ability to sleep for a set time.
- **B tier**: [How to Build Event-Driven Applications: Cloudflare Queues](https://www.youtube.com/watch?v=HXOpxNaKUzw) by [Cloudflare Developers](https://www.youtube.com/@CloudflareDevelopers), 5:19, published 2024-09-26, checked 2026-11-08 against the transcript. Builds an event-driven app with Cloudflare Queues, moving slow work such as sending email out of the request path so each part scales on its own.
- **B tier**: [REST sends data across the network. What if it could send callable objects instead? | Kenton Varda](https://www.youtube.com/watch?v=6ExqctHGuVw) by [JavaScript Conferences by GitNation](https://www.youtube.com/@JavaScriptConferences), 28:56, published 2026-05-21, checked 2026-11-08 against the transcript. Kenton Varda on Cap'n Web, which returns references to live server objects instead of data: promise pipelining, lifecycle management, and why capability-based RPC is a better security model for agents than handing them tokens.
- **C tier**: [Building durable agents with Durable Objects (Cloudflare Connect 2026)](https://www.youtube.com/watch?v=VBsqp3NutAE) by [Cloudflare Developers](https://www.youtube.com/@CloudflareDevelopers), 43:02, published 2026-10-21, checked 2026-11-08 against the description. Justin Schroeder on building an agent cloud entirely on Cloudflare, with Durable Objects as long-lived agents and Workers composing them with storage, queues, models and sandboxed code.
- **C tier**: [Cloudflare Workflows Just Got A Lot Better!](https://www.youtube.com/watch?v=fZ_2bnOvGjQ) by [Cloudflare Developers](https://www.youtube.com/@CloudflareDevelopers), 7:51, published 2026-06-30, checked 2026-11-08 against the transcript. A quick tour of newer Workflows features: human in the loop, sleeping and hibernation, rollbacks, inspecting state locally, and cron triggers.

## Systems thinking

Simplicity, values, specifications, property tests and failure: the ideas under the fence.

- **S tier**: ["Simple Made Easy" - Rich Hickey (2011)](https://www.youtube.com/watch?v=SxdOUGdseq4) by [Strange Loop Conference](https://www.youtube.com/@StrangeLoopConf), 1:01:38, published 2021-09-02, checked 2026-11-08 against the transcript. Rich Hickey separates simple, meaning not braided together, from easy, meaning close at hand, and argues that reliability needs simplicity. The vocabulary behind this stack's uncomplect skill.
- **S tier**: [John Hughes - Testing the Hard Stuff and Staying Sane](https://www.youtube.com/watch?v=zi0rHwfiX1Q) by [ClojureTV](https://www.youtube.com/@ClojureTV), 47:17, published 2014-03-26, checked 2026-11-08 against the transcript. John Hughes shows why example tests cannot keep up with interactions between features and with race conditions, and how QuickCheck tests generated from a state machine model find those bugs and shrink them to a minimal failing case. This is why the stack prefers property and model tests.
- **A tier**: [John Hughes - How to specify it! A guide to writing properties of pure functions | Code Mesh LDN 19](https://www.youtube.com/watch?v=zvRAyq5wj38) by [Code Sync](https://www.youtube.com/@CodeSync), 43:56, published 2019-12-06, checked 2026-11-08 against the description. John Hughes gives five strategies for finding properties of pure functions, compares how well each finds bugs, and names the biggest pitfall. The practical companion to the talk above.
- **A tier**: [Leslie Lamport: Thinking Above the Code](https://www.youtube.com/watch?v=-4Yp3j_jk8Q) by [Microsoft Research](https://www.youtube.com/@MicrosoftResearch), 59:50, published 2014-07-15, checked 2026-11-08 against the transcript. Leslie Lamport argues that every program deserves a specification written before the code, the way a building gets a blueprint, and especially concurrent and distributed ones.
- **A tier**: ["Tackling Concurrency Bugs with TLA+" by Hillel Wayne](https://www.youtube.com/watch?v=_9B__0S21y8) by [Strange Loop Conference](https://www.youtube.com/@StrangeLoopConf), 30:05, published 2017-10-02, checked 2026-11-08 against the transcript. Hillel Wayne introduces TLA+ through practical examples: writing a specification to check a design, and catching race conditions, duplicated money and deadlocks before they reach code.
- **A tier**: [The Value of Values with Rich Hickey](https://www.youtube.com/watch?v=-6BsiVyC1kM) by [InfoQ](https://www.youtube.com/@infoq), 31:43, published 2012-10-08, checked 2026-11-08 against the transcript. Rich Hickey on values: immutable facts you can compare and share, against places you update in place. The same idea sits behind this stack's rule to store source facts and derive the rest.
- **B tier**: [Domain Modeling Made Functional - Scott Wlaschin - KanDDDinsky 2019](https://www.youtube.com/watch?v=2JB1_e5wZmU) by [KanDDDinsky](https://www.youtube.com/@KanDDDinsky), 50:49, published 2019-12-06, checked 2026-11-08 against the transcript. Scott Wlaschin shows how to use types to model a domain so that some incorrect states cannot be written at all. It carries straight over to Effect Schema.
- **B tier**: [Ruby Conf 12 - Boundaries by Gary Bernhardt](https://www.youtube.com/watch?v=yTkzNHF6rMs) by [Confreaks](https://www.youtube.com/@Confreaks), 45:55, published 2012-11-25, checked 2026-11-08 against the transcript. Gary Bernhardt starts from isolated unit tests and works toward a design that makes isolation natural: a functional core of values, wrapped in a thin imperative shell that talks to the outside world.
- **B tier**: ["Systems that run forever self-heal and scale" by Joe Armstrong (2013)](https://www.youtube.com/watch?v=cNICGEwmXLU) by [Strange Loop Conference](https://www.youtube.com/@StrangeLoopConf), 1:10:22, published 2021-03-26, checked 2026-11-08 against the transcript. Joe Armstrong on systems that run for a very long time: isolated processes with private memory that talk only by message passing, expecting crashes and fixing them as they run, and changing the code while it executes.
- **C tier**: [Hammock Driven Development - Rich Hickey](https://www.youtube.com/watch?v=f84n5oFoZBc) by [ClojureTV](https://www.youtube.com/@ClojureTV), 39:49, published 2012-12-16, checked 2026-11-08 against the transcript. Rich Hickey on thinking about a problem for a long time before coding: identifying and understanding it, then letting your background mind work on it while your waking mind steps back.
- **C tier**: ["Transactions: myths, surprises and opportunities" by Martin Kleppmann](https://www.youtube.com/watch?v=5ZjhNTM8XU8) by [Strange Loop Conference](https://www.youtube.com/@StrangeLoopConf), 41:08, published 2015-09-27, checked 2026-11-08 against the description. Martin Kleppmann on what transactions are for, why they got a reputation for being slow, and the newer algorithms that make them scale. Background for choosing what a store guarantees.