Why Reddit Hates Caching APIs with useMemo in 2025

The Alluring Trap of useMemo for API Calls

The temptation to use useMemo for data fetching stems from a misunderstanding of its core purpose. The React documentation defines useMemo as a hook that lets you cache the result of a calculation between re-renders. The key word here is calculation. A calculation should be a pure function: given the same input, it always returns the same output without causing side effects.

An API call is the polar opposite of a pure calculation. It's a side effect. It interacts with the outside world (a network), its result can change even with the same inputs (updated data on the server), and it's inherently asynchronous. Forcing this square peg into the round hole of useMemo leads to a host of problems.

The Technical Debt: 5 Reasons useMemo is the Wrong Tool

When you use useMemo for fetching, you're not just writing suboptimal code; you're actively creating problems for your future self and your team. Here’s why it's a well-established anti-pattern.

1. It's a Hint, Not a Guarantee

This is the most critical flaw. The React docs are explicit: "React may choose to ‘forget’ some previously memoized values and recalculate them on next render." This can happen for various reasons, such as freeing up memory. If your API call is inside useMemo, React could decide to discard your "cached" data at any moment, triggering an unnecessary and unexpected network request. This makes your application's behavior unpredictable and inefficient.

2. The Nightmare of Manual State Management

A data fetch isn't a single state; it's a state machine. You need to know if it's currently loading, if it succeeded, if it failed, and what the error was. With a useMemo approach, you're suddenly responsible for managing all this yourself, typically with a collection of messy useState hooks:

const [isLoading, setIsLoading] = useState(true);
const [error, setError] = useState(null);
const [data, setData] = useState(null); // Wait, isn't useMemo supposed to hold the data?

This boilerplate clutters your components and has to be rewritten for every single data-fetching requirement, introducing more opportunities for bugs.

3. Memoization is Not Caching

It's crucial to understand the difference.

• Memoization (useMemo): Scoped to a single component instance. When the component unmounts, the memoized value is gone forever. If another component needs the same data, it has to fetch it all over again.
• Caching (Dedicated Libraries): A global, persistent storage layer. Data fetched by one component is instantly available to any other component that requests it. The cache outlives component lifecycles, surviving navigations and re-mounts, which dramatically improves performance and user experience.

4. Race Conditions and Stale Data

What happens if a dependency in your useMemo changes quickly? You could trigger a second request before the first one has finished. A naive implementation won't know how to handle this. It might display data from the first request, only to have it overwritten by the second, or vice-versa if the first request resolves later. Furthermore, useMemo has no concept of keeping data fresh. It won't automatically refetch when the user re-focuses the browser tab or when the network connection is restored.

5. It Breaks React's Rules

Placing a side effect like a fetch call directly inside the body of useMemo violates the principles of React's render phase. The render phase should be pure and predictable. Side effects belong in useEffect (for simple cases) or, preferably, in dedicated hooks provided by data-fetching libraries that manage these effects correctly.

The Modern Standard: Dedicated Data-Fetching Libraries

The React ecosystem has matured significantly. The community's consensus is to delegate server state management to libraries built specifically for that purpose. These tools handle all the complexity we've discussed out of the box.

The most popular choices in 2025 are:

• TanStack Query (formerly React Query): Often considered the gold standard for its powerful caching, background refetching, and devtools.
• SWR: A lightweight and excellent alternative from Vercel, based on the "stale-while-revalidate" caching strategy.
• RTK Query: Part of the official Redux Toolkit, it's a great choice for teams already invested in the Redux ecosystem.
• Apollo Client: The go-to solution for applications using GraphQL.

These libraries aren't just utilities; they are comprehensive state management solutions for your server data.

Comparison: The DIY useMemo Approach vs. React Query

Practical Refactor: From useMemo Hell to React Query Heaven

Let's see how much cleaner and more powerful our code becomes. Here's a typical, flawed attempt at using useMemo and useEffect.

Before: The Anti-Pattern

// In your component
const [itemId, setItemId] = useState(1);
const [data, setData] = useState(null);
const [isLoading, setIsLoading] = useState(false);
const [error, setError] = useState(null);

useEffect(() => {
  const fetchData = async () => {
    setIsLoading(true);
    setError(null);
    try {
      const response = await fetch(`https://api.example.com/items/${itemId}`);
      if (!response.ok) throw new Error('Network response was not ok');
      const result = await response.json();
      setData(result);
    } catch (e) {
      setError(e);
    } finally {
      setIsLoading(false);
    }
  };

  fetchData();
}, [itemId]); // This is better than useMemo, but still a lot of boilerplate.

After: The Modern Solution with TanStack Query

import { useQuery } from '@tanstack/react-query';

const fetchItem = async (itemId) => {
  const response = await fetch(`https://api.example.com/items/${itemId}`);
  if (!response.ok) throw new Error('Network response was not ok');
  return response.json();
};

// In your component
const [itemId, setItemId] = useState(1);
const { data, isLoading, isError, error } = useQuery({
  queryKey: ['item', itemId],
  queryFn: () => fetchItem(itemId),
});

Look at the difference. We replaced a dozen lines of brittle, manual state management with a single, declarative hook. All the complexity of caching, loading states, and error handling is now managed by the library, leaving our component code clean, readable, and focused on its primary job.

Conclusion: Embrace the Right Tools for the Job

The reason Reddit—and the wider React community—is so vocal about this topic is to help developers avoid common pitfalls. Using useMemo for API calls is a classic example of using a tool for a purpose it was never designed for. It might seem to work for a trivial case, but it doesn't scale and ignores years of collective experience in solving the complex challenge of managing server state in a client-side application.

In 2025, the debate is settled. For robust, performant, and maintainable React applications, turn to dedicated data-fetching libraries like TanStack Query or SWR. They provide the right abstractions for the job, improve developer experience, and lead to a much better end-product for your users.