API Tech Jargon for Product Leaders - Sketched & Explained

Check out our post on full-stack system design to understand how architecture, APIs, databases, and cloud all fit together if you want to understand the bigger picture before you dive into this post about APIs specifically

Looking for a way to understand technical jargon around Application Programming Interfaces (APIs)?

Here’s how I’d sketch it out and explain it to non-technical product leaders.

Architecture – API concepts you must know

APIs allow software systems to communicate or "talk" to each other.

Internal APIs enable communication between layers within your product — like the frontend User Interface (UI) layer and backend business logic layer.

If you're shaky on your understanding with the 3 layers and high-level system design and architecture and want a primer before diving into this section about APIs, read my explainer on high-level technical jargon explained for non-technical product leaders first.

Internal APIs are useful because they:

• Decouple layers so they can evolve independently
• Expose backend business logic to multiple consumers like web apps, mobile apps, and admin portals

For example, internal APIs allow both your pet adoption admin portal and your consumer-facing Web, iOS, and Android apps to show the same list of senior pets — without needing to build the backend logic for defining a “senior pet” three times.

External APIs enable your product to communicate with 3rd party tools, products, and services.

External APIs are useful because they let you integrate specialist functionality into your product without building it from scratch.

For example, external APIs allow you to schedule home inspections within your product using Google Calendar — without needing to build your own calendar system.

Communication – Build your technical fluency around APIs

Types of APIs

There are several types of APIs based on how they’re structured and consumed:

• REST (Representational State Transfer) is the most common style for web and consumer applications. It structures requests around predictable URLs and HTTP verbs (GET, POST, PUT, PATCH, and DELETE).
• SOAP (Simple Object Access Protocol) is older and more rigid, but still used in enterprise systems that need strict security and contract guarantees.
• GraphQL (Graph Query Language) allows clients to specify exactly what data they need in a single request. It's used for data-rich apps where different consumers may want different pieces of information at once.
• gRPC, Webhooks, and Software Development Kits (SDKs) are used in specific technical scenarios.

For example, your pet adoption app could use a REST API to fetch pets, while different shelters that integrate with your product could use GraphQL to fetch only the specific pet details they want to show on their adoption pages.

Documenting APIs

Clear documentation allows for faster integration and fewer bugs.

• OpenAPI (formerly Swagger) is a well defined standard with strong integration to tools like code editors.
• API playgrounds provide real-time interactive request and response scenarios.

For example, if your team documents your API for shelters to also show pets available for adoption on their apps, building Swagger documentation and an API playground lets their engineers explore and test how to fetch available pets without needing to write any code upfront.

Performance & Scalability

Rate limiting prevents overload by capping the number of requests in a certain amount of time.

For example, if a rogue script tries to scrape pet listings thousands of times per minute, rate limiting could protect your API and infrastructure.

Caching increases API performance (quicker response, lower load) by storing the results of a query instead of needing to fetch a new copy each time. 

This reduces latency, improves usability and increases uptime which improves reliability.

For example, you could cache the list of available pets for an hour so that each user doesn't trigger a new database call.

Stateless APIs don't store session data between requests, which make them easier to scale horizontally.

For example, the API that fetches available pets doesn’t need to remember whether users are on page 1 or 5 because the client app can specify which page of pets to fetch each time.

API monitoring proactively detects performance issues, failed integrations, and downtime.

For example, if your Google Calendar integration for scheduling home inspections suddenly starts failing, monitoring would alert your team before users begin reporting issues.

Securing APIs

API security is critical and there are two important aspects:

• Authentication confirms users are who they say they are
• Authorisation confirms that users are allowed to do what they're trying to do

For example, authentication confirms that a shelter user can access the admin portal. Authorisation ensures volunteers can add or edit pet profiles — but only shelter admins can delete them.

Common authentication and authorisation methods include:

• OAuth – Allows users to authorise apps without sharing login credentials, which can be used for signing in with social platforms like Facebook
• JWT (JSON Web Tokens) – A compact, secure way to transmit identity and permissions, often used in OAuth-based authentication flows
• API keys – Used for server-to-server authentication, like your backend interacting with a payment processing gateway

Design Principles

RESTful APIs follow a predefined structure to make them easier to understand and integrate with. They are based on HTTP verbs, each with specific behaviour:

• GET – Fetches data
• POST – Creates a new record
• PUT – Replaces an existing record entirely
• PATCH – Updates only certain fields in an existing record
• DELETE – Removes a record

For example, GET returns a list of pets available for adoption and can be used by both the shelter admin portal and consumer app.

POST could create a new pet profile when a shelter adds a pet for adoption.

PATCH could be used to update specific fields in a pet's profile like their age and breed without changing other profile fields.

PUT could be used to replace a pet’s entire profile, for example, if a shelter admin quickly creates a placeholder profile for "Dog75" while capturing in bulk, then a volunteer can later update it fully with photos, bio, and adoption details.

DELETE removes a record, for example, after accidentally capturing a duplicate of the same pet.

Planning – Build your technical intuition around APIs

It’s often cheaper to pay for access to specialist functionality via third-party APIs than to build it from scratch, especially for new features where you're still trying to find product-market fit.

Prefer integrating with well documented APIs and ensure that your product documents its APIs well, especially if you're exposing them to the market.

For example, if you're integrating in-app payments for adoption fees, prefer integrating with well documented APIs for payment processing like Stripe since robust documentation makes integration seamless and faster.

If you're creating APIs for external products to use:

• Prioritise building robust documentation
• Dedicate time in your roadmap to polish and test them
• Define your target audience clearly, so you choose the right type of API (REST, SOAP, or GraphQL)

For example, if you offer an API for shelters to sync their pets available for adoption with your product, robust documentation allows them to integrate seamlessly with your APIs and defines thresholds around performance and uptime.

If you're able to define performance metrics upfront, do so. But it can be tricky, so leverage real-world usage data over time to identify and prioritise bottlenecks for scaling and optimisation.

For example, you won't know upfront how users will interact with your "catalogue" of pets available for adoption and viewing those pets' details.

They may prefer clicking into each pet as they scroll to learn more, or they may "wishlist" several pets while scrolling and only later dive into each one to learn more.

Real-world usage data can guide engineering on whether to change the APIs to return more pets for the home screen at once with fewer details (if users mostly "wishlist" several pets while quickly scrolling), or fewer pets with full details (if users mostly click to learn more about each pet as they scroll).

Okay, and that’s a wrap.

If you liked this style of sketched & explained knowledge share, either check out our post on databases and data storage technical jargon - sketched and explained, or download your FREE copy of our no-fluff ebook System design, APIs, and databases sketched & explained before lunch

Whenever you're ready, here's how I can help you

System design, APIs, and databases sketched and explained before lunch - FREE

Download your free copy of our ebook and build your intuitive technical fluency around 3 core concepts of building software products to earn engineers' trust FAST

Product Tech Sense™ Framework - PREMIUM

Request an invite to our limited-seats, premium, online live cohorts to master technical fluency, build technical intuition, and earn engineers' trust with our guided, high-touch sessions