Experience with Application Programming Interfaces (APIs)

API Testing

At TIAA, I tested APIs by simulating real-world scenarios to ensure seamless integration with our systems. These tests verified that the APIs delivered accurate and timely data, maintaining the reliability and integrity of our financial applications.

Understanding JSON and JavaScript Objects in relation to APIs

JSON stands for JavaScript Object Notation. It is a lightweight data format used to structure data as key-value pairs. JSON is both human-readable and easy for machines to parse and generate, making it the most common format for modern APIs.

A typical JSON structure closely resembles a JavaScript object—a foundational data type in JavaScript. JSON objects can be directly used in code to access and manipulate data. JSON is particularly useful when working with data that needs to be easily consumed by both humans and machines.

Example: Stock Data in JSON Format

Below is a sample JSON response from a stock market API. This format is similar to the ones I worked with while validating fund profiles at TIAA. 

{
  "symbol": "AAPL",
  "companyName": "Apple Inc.",
  "latestPrice": 150.25,
  "change": -1.35,
  "changePercent": -0.89,
  "high": 152.00,
  "low": 148.50,
  "open": 149.00,
  "volume": 74321512,
  "marketCap": 2489680000000,
  "peRatio": 28.45,
  "lastTradeTime": "2025-05-09T16:00:00"
}

Fund Profiles at TIAA

In addition to stock data, I also worked extensively with APIs to retrieve and validate fund profile data for a variety of investment products available on the TIAA platform.

Fund Type Description User Persona (Investor Persona)
Target-Date Funds Adjust investments based on the target retirement date. Ideal for long-term investors who want a hands-off, age-appropriate strategy that rebalances over time.
Mutual Funds Pool investor funds into diversified portfolios of stocks, bonds, or other securities. Great for investors looking for diversification and professional fund management.
Variable Annuities Investments that provide income based on market performance and offer potential for growth. Suited for individuals seeking growth potential with optional income guarantees in retirement.
Fixed Annuities Provide guaranteed income and are not subject to market fluctuations. Best for risk-averse retirees who want steady, predictable income.
Bond Funds Invest in bonds and provide income with lower risk. Appeals to conservative investors focused on capital preservation and income.
Balanced Funds A mix of stocks and bonds to balance growth and risk. Good for moderate investors who want a mix of safety and growth.
Money Market Funds Provide stability and liquidity, investing in short-term debt. Great for short-term savers or those parking cash temporarily with minimal risk.
International Funds Invest in non-U.S. markets for global diversification. Ideal for investors looking to diversify beyond the U.S. and tap into global opportunities.
TIAA Real Estate Invests in residential and commercial real estate for diversified exposure. Attractive to investors seeking alternative assets for long-term stability and income.
FDIC Insured Products Savings and CD products insured by the Federal Deposit Insurance Corporation (FDIC). Perfect for highly conservative investors or those near retirement who prioritize safety over growth.

How TIAA & Other Firms Use APIs

  • API as a Communication Bridge: An API (Application Programming Interface) enables communication between different software systems, allowing one system to request and retrieve data from another system.
  • Request and Response Process: When a user interacts with an application, the system sends a request to an API. The API queries the backend system (like a database or service), retrieves the necessary data, and sends it back to the application for display.
  • Real-Time Data Access: APIs ensure that applications have access to the most current, accurate data, such as portfolio details, fund performance, or transaction history, in real time.
  • Cross-Team Collaboration: The APIs built and maintained by our Scrum team at TIAA were leveraged by various other teams across the firm, enabling them to integrate real-time data and enhance the functionality of their own applications, creating a unified and consistent data experience throughout the organization.

Try out this simple demo Weather API app I built.

For demonstration and educational purposes only.

  • User Input: Enter a city name in the input field of the app below and click “Search” to initiate the process.
  • API Call: The app uses JavaScript's `fetch()` method to send a request to the OpenWeatherMap API, passing in the city and an API key.
  • Data Handling: The API responds with weather details such as temperature, conditions, and an icon that visually represents the current weather.
  • Display: The app parses the JSON response and displays the weather data dynamically below the search box.
  • Try It Out: You can test the app right below to check real-time weather conditions in any city around the world.

Simple Weather App

Try out this simple demo Stock API app I built.

For demonstration and educational purposes only.

  • User Input: Enter a stock ticker symbol (like AAPL, MSFT, or TSLA) into the input field and click “Search” to start.
  • API Call: The app uses JavaScript’s fetch() method to query a stock market API, passing the ticker and API key.
  • Data Handling: The response includes real-time data like price, volume, day change, and more, returned in JSON format.
  • Display: The app parses the JSON and updates the UI dynamically with clean, readable stock information.
  • Try It Out: Use the app below to check real-time stock data by entering different company ticker symbols.

Simple Stock Screener App