CRUD Is Everything

CRUD, Functions, and Triggers

In Lesson 1, you learned that every computer is built from two building blocks: storage and compute. That is what a computer is. Now let's talk about what a computer does.

Turns out, there are only four operations. Ever. Let's get into it.

CRUD: The Only 4 Things

Here is the challenge. Think of anything you have ever done on a computer. Anything. Sending an email. Editing a photo. Scrolling Instagram. Playing a game. Ordering food.

Nothing falls outside these four categories:

• Create means making something new that didn't exist before
• Read means retrieving and looking at existing data
• Update means changing something that already exists
• Delete means removing something permanently

That is it. There is no fifth operation. Every single thing you have ever done on a computer maps to one of these four.

Post something on Instagram? Create. Open your email? Read. Edit a typo in a Google Doc? Update. Remove an old file? Delete.

Even within a single task, you are chaining CRUD operations. Writing a Google Doc: you Create the document, you Create each letter as you type, you Update a letter when you fix a typo, you Delete a paragraph you don't want, you Read it when you proofread, and when you share it, that is a Create (a new copy/link for the recipient).

Here's the flow of data through any system, from storage, through processing, to screen:

Every app you use is just this pattern on repeat. Netflix Reads its catalog from a database and shows you thumbnails. Uber Creates a ride request, Reads nearby drivers, Updates the ride status as the driver moves, and Deletes the request once you arrive.

The To-Do List: Your Canonical Exercise

Here is the exercise that proves CRUD is real. If you can describe a to-do list by breaking it into atomic pieces, you can describe anything.

A to-do list app does exactly four things:

1. Create a new task ("Buy groceries")
2. Read the list of tasks (display them on screen)
3. Update a task (mark it complete, edit the text)
4. Delete a task (remove it from the list)

That is the entire app. There is nothing else it does. Every feature you could imagine adding (due dates, priorities, categories, sharing) is just more CRUD on more data. A due date is an Update to a task. A category is a Create of a label plus an Update to attach it. Sharing is a Create of a permission record.

This is why the to-do list is the "Hello World" of app building. It is the smallest possible app that exercises all four operations. If you can break a to-do list into CRUD, you can break a CRM into CRUD. You can break an inventory system into CRUD. You can break anything into CRUD.

Functions: What Computers Actually Run

So if CRUD is what happens, then a function is how it happens. A function is a set of instructions that performs one or more CRUD operations.

Think of it like cooking. CRUD is the set of techniques (baking, frying, boiling, steaming). A function is a recipe that uses those techniques. You don't "do baking AND follow recipes" as two separate activities. You follow a recipe (function) that tells you to bake (CRUD operation). Functions perform CRUD operations. They are not two separate things a computer does. A function is the vehicle; CRUD is the action.

Here is what a function looks like conceptually:

function sendWelcomeEmail(newUser) {
  userData = READ from database where id = newUser.id
  email   = CREATE an email using userData
  result  = CREATE a send-request to the email service
  LOG     = CREATE a record that we sent the email
}

Four lines, three Creates and a Read. That is a function. Every piece of software you have ever used is just functions performing CRUD operations, all the way down.

Triggers: What Kicks Off a Function

Functions don't run by themselves. Something has to trigger them. Something has to say "go." There are four types of triggers:

1. Manual. A human does something. Clicks a button, submits a form, hits enter. The most intuitive trigger.

2. Cron / Schedule. A timer that fires at a set time. "Every weekday at 8 AM, run this function." Like an alarm clock for code. The name "cron" comes from the Greek word for time (chronos).

3. Webhook. An external service sends your system a message. "Hey, something happened on my end that you should know about." It is like a doorbell: something rings, your function answers.

4. Event-driven. A change in data automatically fires a function. "Whenever a new row appears in this database table, run this function." No human involved, no schedule. The data change itself is the trigger.

Why This Matters: Describing Software to AI

Now it all connects. You just learned three concepts:

1. CRUD, the only four operations
2. Functions, sets of instructions that perform CRUD
3. Triggers, what kicks off functions (manual, cron, webhook, event)

With just this vocabulary, you can describe almost any software system. And that description, in plain English using these terms, is exactly what you give to an AI like Claude to build the actual code.

You don't need to know how to code. You need to know what the code needs to do. The vocabulary you just learned is the bridge.

// Cloud Run function triggered by Cloud Scheduler
// Cron: "0 15 * * 5" (Fridays at 3 PM)

async function generateWeeklyReport() {
  // READ: get usage data from database
  const usage = await db.query(
    "SELECT * FROM usage_data WHERE week = current_week()"
  );

  // CREATE: generate summary with AI
  const summary = await claude.messages.create({
    model: "claude-sonnet-4-5-20250514",
    messages: [{ role: "user", content: formatPrompt(usage) }],
  });

  // CREATE: send the email
  await email.send({
    to: "team@company.com",
    subject: "Weekly Report",
    body: summary.content,
  });
}

Further Reading