Making 4 APIs Race Each Other (ZyMerge)

I got tired of opening 4 tabs to find stock photos. So I made them race.

The Problem

Designers search Unsplash. No good results. Try Pexels. Nothing. Pixabay. Still looking. That's 3 minutes gone for one image.

The Solution

One search. Four APIs. First results win.

async function searchEverywhere(query: string) {
  const results = await Promise.allSettled([
    searchUnsplash(query),
    searchPexels(query),
    searchPixabay(query),
    searchNASA(query), // Yes, NASA. Space photos are cool.
  ]);

  // Don't let one slow API ruin everything
  return results
    .filter((r): r is PromiseFulfilledResult<Image[]> =>
      r.status === 'fulfilled'
    )
    .flatMap(r => r.value);
}

Promise.allSettled is the hero here. One API times out? Who cares. Show the rest.

The Normalization Nightmare

Every API returns different data:

// Unsplash
{ urls: { regular: '...' }, user: { name: '...' } }

// Pexels
{ src: { large: '...' }, photographer: '...' }

// Pixabay
{ webformatURL: '...', user: '...' }

// NASA
{ url: '...', title: '...' }

So I made them all speak the same language:

interface UnifiedImage {
  id: string;
  source: 'unsplash' | 'pexels' | 'pixabay' | 'nasa';
  url: string;
  thumbnail: string;
  credit: string;
}

Four adapters. One interface. Sanity preserved.

Real-Time Favorites with Convex

Wanted favorites to sync across devices instantly. Convex made this stupid simple:

export const toggleFavorite = mutation({
  args: { imageId: v.string(), imageData: v.any() },
  handler: async (ctx, { imageId, imageData }) => {
    const user = await ctx.auth.getUserIdentity();

    const existing = await ctx.db
      .query('favorites')
      .filter(q => q.eq(q.field('imageId'), imageId))
      .first();

    if (existing) {
      await ctx.db.delete(existing._id);
    } else {
      await ctx.db.insert('favorites', { userId: user.subject, imageId, ...imageData });
    }
  },
});

No REST endpoints. No manual cache invalidation. Just works.

The NASA Bonus

Added NASA's Image API as a joke. Turned out to be everyone's favorite feature. Space photos hit different.

Performance Numbers

4 APIs searched in parallel: ~400ms average
Slowest API doesn't block results
Favorites sync: instant

Try it: zymerge.vercel.app

The source is on GitHub if you want to see how the sausage is made.