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Infrastructure as effects

Sam relates runtime clients, business logic, infrastructure policies, and deployed resources in one typed program²⁷. The compiler can check these relationships before deployment.¶

Contract → surfaces

A contract²¹ defines shared input, output, failures, and metadata. Projections turn registered capabilities into command line, HTTP, MCP tools, browser RPC, and code mode²³ surfaces. Each surface²⁶ derives its input and failure definitions from the same schemas.¶

Code → bindings → resources

A client operation can imply a policy requirement supplied when the function is built. Sam describes bindings²⁵ as permissions and environment variables together at 37:09. An Alchemy Layer can declare the cloud resources behind a service. The Stack⁸ declares cloud resources.¶

Worked example: a D1 Layer

In the database cartridge³⁸, makeD1Vendor declares SQLite migrations and a D1 database. The database declaration receives those migrations through its migrations option.¶

const makeD1Vendor = Effect.fn("makeD1Vendor")(function* makeD1Vendor({
  id,
}: D1Options) {
  const migrations = yield* Drizzle.Schema(`${id}-d1-schema`, {
    dialect: "sqlite",
    out: databaseMigrationDirectory("d1"),
    schema: databaseSchemaFile("d1"),
  });

  const database = yield* Cloudflare.D1.Database(`${id}-d1`, { migrations });

  return { _tag: "D1" as const, database };
});

D1(options) builds the Layer below. It combines RunLogLayer(vendor) with the DatabaseVendor service and provides QueryDatabaseBinding. The package keeps its database declaration and service construction³⁰ together.¶

export const D1 = (options: D1Options) =>
  Layer.unwrap(
    Effect.gen(function* buildD1Layer() {
      const vendor = yield* makeD1Vendor(options);

      return Layer.mergeAll(
        RunLogLayer(vendor),
        Layer.succeed(DatabaseVendor, vendor)
      );
    })
  ).pipe(Layer.provide(Cloudflare.D1.QueryDatabaseBinding));

Trace the declaration first, then the returned Layer. Read Database¹¹ for its current callers and local verification commands.¶

Plan → review → deploy

A plan model⁸ describes infrastructure changes before they apply. Sam connects Effect purity with a reviewable plan and a concrete deployment result at 12:22. Tests using real infrastructure check behavior after deployment at 16:01.¶

The compiler checks the joins

Effect⁹ tracks required services in its type. Effects and Layers let the type system track the resource providers a Stack needs at 07:01. Sam describes a type error when code still requires a removed binding²⁵ at 15:25. The compiler can check these relationships before deployment: Happy Path 116, 28:00.¶

Cartridges

A cartridge³⁸ is a package that owns one job and the resources it needs. Replacing its Layer changes the implementation and dependencies without changing callers.¶

Lifecycles

Use an XState machine²⁷ for named states, retries, cancellation, or a lifecycle to resume or inspect. Model the states and the events that move between them.¶

The fence

The fence⁵⁰ is the compiler checks, lint rules, tests, and hooks that enforce project rules. These rules cannot establish whole-program behavior.¶

Cloud as a library

Sam’s phrase is that the whole cloud becomes a library⁶, at 29:50. He argues that infrastructure tools can retain application-code properties such as debugging and tests at 03:50.¶

The joins at a glance

• Contract → surfaces:
  • What the program checks: Shared input and failure schemas¶
  • Where to read more: One capability, every surface²¹¶
  ¶
• Code → bindings → resources:
  • What the program checks: Required services and resource providers¶
  • Where to read more: Bindings²⁵ · Infrastructure as Effects, Office Hours 27⁸¶
  ¶
• Plan → review → deploy:
  • What the program checks: Changes before application; real-infrastructure behavior after deployment¶
  • Where to read more: Plan model⁸¶
  ¶
• Compiler → joins:
  • What the program checks: Relationships before deployment; code that requires a removed binding¶
  • Where to read more: Happy Path 116⁸¶
  ¶
• Cartridges³⁸:
  • What the program checks: Removal leaves no loose resources or broken imports¶
  • Where to read more: Cartridges³⁸¶
  ¶
• Lifecycles:
  • What the program checks: Named states and the events between them¶
  • Where to read more: Lifecycles are machines²⁷¶
  ¶
• Fence⁵⁰:
  • What the program checks: Project rules; whole-program behavior remains outside these checks¶
  • Where to read more: The fence⁵⁰¶
  ¶
• Cloud as a library⁶:
  • What the program checks: Debugging and tests for infrastructure code¶
  • Where to read more: Cloud as a library⁶¶
  ¶

Last changed 2026-11-08 in 9196534. Source on GitHub. Change log.