API
Also: API, Application Programming Interface, interface de programmation applicative, web API, REST API
Application Programming Interface: a standardised interface that lets applications communicate and exchange data without knowing each other's internal workings.
What it is
An API (Application Programming Interface) is a standardised contract that lets one piece of software request data or actions from another. It defines the available operations, the inputs each one expects, and the outputs it returns. The consumer does not need to understand the internal code of the provider: it only needs to follow the published rules.
Think of an API as a menu in a restaurant. You choose from defined dishes (endpoints), place an order with specifics (parameters), and receive a predictable result. The kitchen (the underlying system) stays hidden.
Why it matters
APIs are the connective tissue of modern digital operations. They matter because they enable:
- Integration: connect a CRM, an accounting tool, and a website without custom rebuilds.
- Automation: replace manual data copying with reliable machine-to-machine flows.
- Scale and reuse: one well-designed API can serve web apps, mobile apps, and partners.
- Ecosystems: expose capabilities so external developers and partners can build on your platform.
For executives, APIs are strategic. They determine how quickly teams ship products, how easily you switch vendors, and whether data can flow across silos.
How it is used in practice
Most modern APIs are REST or GraphQL over HTTPS, exchanging data as JSON. Access is usually controlled with API keys or OAuth tokens, and providers enforce rate limits to protect their systems. Common patterns include:
- Reading data (for example, list customers created this month).
- Writing data (for example, create an invoice).
- Triggering actions (for example, send a payment or run a model).
Concrete worked example
Suppose finance wants daily revenue in a dashboard. Instead of exporting spreadsheets, the dashboard calls the payment provider's API:
1. It sends an authenticated GET request to `/v1/transactions?date=2024-06-01`.
2. The provider validates the token and checks the rate limit.
3. It returns JSON: a list of transactions with amounts, currencies, and statuses.
4. The dashboard aggregates the figures and displays them, refreshed automatically.
The same pattern powers an AI use case: an application sends a prompt to a large language model's API and receives generated text, with usage billed per token.
Key takeaways
- APIs are contracts, not products; stability and documentation are what make them valuable.
- They enable buy versus build decisions and reduce vendor lock-in when standardised.
- Security, versioning, and rate limits are the practical details that decide reliability.
Frequently asked questions
What is an API in simple terms?
An API (Application Programming Interface) is a standardised contract that lets one piece of software request data or actions from another. It defines the available operations, the inputs each expects, and the outputs returned. The consumer follows the published rules without needing to know anything about the provider's internal code.
Why should an executive care about APIs rather than leaving them to the tech team?
Because APIs determine how fast teams ship, how easily you can switch vendors, and whether data crosses internal silos. They make integration between a CRM, an accounting tool and a website possible without custom rebuilds, and they turn manual data copying into machine-to-machine flows. They also decide whether partners and external developers can build on top of your platform.
What is the difference between REST and GraphQL?
Both are styles for exposing an API over HTTPS, most often exchanging data as JSON. REST organises access around fixed endpoints, each returning a predefined shape of data; GraphQL lets the consumer describe in a single query exactly which fields it wants. The choice affects how many calls a client needs and how much unused data travels over the network.
How does a dashboard actually pull data through an API?
Take a finance dashboard that needs daily revenue from a payment provider. It sends an authenticated GET request to an endpoint such as /v1/transactions?date=2024-06-01; the provider validates the token and checks the rate limit, then returns JSON listing transactions with amounts, currencies and statuses. The dashboard aggregates those figures and refreshes automatically, with no spreadsheet export involved.
What technical details decide whether an API is reliable in production?
Security, versioning and rate limits. Access is normally controlled with API keys or OAuth tokens, and providers cap the number of calls to protect their own systems, so an integration must handle those limits. Since an API is a contract rather than a product, stability of that contract and quality of the documentation are what make it worth depending on.