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L21. Designing Your Own REST API

CSCI 344: Advanced Web Technologies

Spring 2026

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Announcements

  1. Tutorial 11 Friday (4/17): You will be designing your REST API based on the app you plan to make. Please attend!
  2. Homework 4 (React) is due Monday (4/20)
  3. Your Project Proposal and wireframe is due next Wednesday (4/22)

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Outline

  1. Services, hosts, and ports
  2. Databases
  3. Building a REST API

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Outline

  • Services, hosts, and ports
  • Databases
  • Building a REST API

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What is a service?

  • What are some examples of services we’ve already been using in this class?
  • A service is a program that runs in the background and listens for / responds to certain kinds of messages.
  • Performs automated tasks, responds to hardware events, or listens for data requests from other software.
  • Often loaded automatically at startup, and run in the background, without user interaction

On a Mac: lsof -i -P | grep -i "listen"

On a Windows: Control Panel > Administrator Tools > Service Icon

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What is a port?

  • Ports are managed by the operating system
  • Each port can be associated with a specific process or service
  • Ports allow computers to differentiate between different kinds of traffic from the same IP address: emails go to a different port (25) than webpages (80), for instance, even though both reach a computer over the same Internet connection.
  • Some ports are reserved and some are open

Read more here

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What is an http://127.0.0.1?

  • 127.0.0.1 is a special IP address – also referred to as “localhost” – which is a reference to your local computer.
  • Doesn't let computers communicate with other devices as a real IP address does (it’s private, not public)
  • On most operating systems, the following two addresses can be used interchangeably:

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What is a web server

Web servers are services that are listening to HTTP traffic. They are constantly running (i.e., an infinite event loop) and listening to incoming traffic.

  • Web traffic (HTTP) is typically routed to port 80 (that’s a standard)
  • Encrypted web traffic (HTTPS) is typically routed to port 443 (that’s also a standard).

In Tutorial 11, you are going to create one of these web services that listens for traffic.

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How does GitHub Pages work?

  • How does GitHub Pages work?
    • How do the files you push to GitHub end up on one of GitHub’s web servers?
  • What kinds of resources does GitHub Pages serve?
  • What kinds of resources does it not it serve?

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Static Web Page

Architecture

(Homework 2)

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Outline

  1. Services, hosts, and ports
  2. Databases
  3. Building a REST API

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What is a database?

A database is an organized collection of structured information, or data, typically stored electronically in a computer system.

​

How is this better than just storing data in a text file?

​

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Why would you want to use a database?

  • ​

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Why would you want to use a database?

  • Organizing your data: Strategies for grouping like entities together.
  • Enforcing data validation and integrity rules
  • Transaction management: if multiple people are altering the same data instance at the same time, the database will help organize these requests so that they don’t collide with each other
  • Indexing: Databases also have infrastructure for building binary search trees to speed up queries (so that searches can be done in O(logn) time).
  • SQL: Relational databases also understand SQL – a declarative language that allows a user to define the structure of a database, and to “CRUD” data.

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Types of Databases

There are many different kinds of databases, but the two most common “families” of databases are:

  1. Relational Databases
  2. NoSQL Databases

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Types of Databases: Relational (SQL) Databases

  • Approach: Data is organized into tables with predefined schemas, where rows represent records and columns represent fields.
  • Examples: PostgreSQL, Oracle, Microsoft’s SQL Server, MySQL, SQLite)
  • Strengths:
    • Ensures data integrity with transactions (ACID Compliance)
    • Structured Query Language (SQL): Industry standard for querying data.
    • Excellent at asking questions across multiple resources / collections. For instance: “which employees earned > $50K in revenue this week in under 40 hours?
  • Weaknesses:
    • Can be overkill for data that is fairly unstructured (e.g., storing chat messages, etc.)
    • Scalability: Hard to scale for very large datasets

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Types of Databases: NoSQL Databases

  • Approach: A non-tabular database designed for flexibility, with different models (e.g., document, key-value, column-family, graph).
  • Examples: MongoDB, Firebase, CouchDB (document stores), Redis (Key-Value Stores, Neo4j (Graph databases)
  • Strengths:
    • Flexibility: Schema-less design allows storing unstructured and semi-structured data.
    • Scalability: Designed for distributed architectures.
    • Optimized for high-volume, low-latency operations.
  • Weaknesses:
    • Consistency: Availability over consistency
    • Limited support for complex queries across documents / resources.

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Your REST API will use a database

You will be using SQLite to organize your data.

  • It’s a very simple database designed for learning and simple data organization and retrieval tasks
  • The entire database is stored in one file
  • You will be able to inspect your database directly from VS Code

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Outline

  • Services, hosts, and ports
  • Databases
  • Building a REST API

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Building a REST API

What kinds of things do we need to think about when building a REST API?

  • What resources are important?
  • What data fields should each resource have?
  • Who can access those resources (read / write)?
  • What should we name the endpoints?

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Server-Side Architecture

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Activity: Design an Online Shoe store

You are going to design an API blueprint for an online show store. Therefore, you’re going to have to make some decisions about:

  • What resources your system needs
  • What endpoints exist
  • What fields each endpoint needs
  • Which fields can be queried
  • Who is allowed to use each endpoint

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Let’s keep it simple

This system can be complex, but let’s keep it simple by only designing allowing the user to interact with 3 Resources:

  • Sneakers
  • Favorites
  • Orders

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Sneakers

  • Endpoint address: /api/sneakers
  • Data fields & types?
  • Which data fields are searchable?
  • Who should be able to see the data (the world, only some users)?

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Favorites

  • Endpoint address:
  • Data fields & types?
  • Which data fields are searchable?
  • Who should be able to see the data (the world, only some users)?

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Orders

  • Endpoint address:
  • Data fields & types?
  • Which data fields are searchable?
  • Who should be able to see the data (the world, only some users)?

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Let’s build this thing!

npm install # installs dependencies

npm run generate # generates the API from the YAML file

npm run seed # inserts some fake data

npm run dev # starts the server

ngrok http 3100 # Sarah-only: share with the class…