Cache stampede (JavaScript)

cache-stampede.js

// Basically, store a promise for a key, and return that promise for its key, until the async job is done.

const refPromises = {};

const workflowWithOneCacheMiss = async (key) =>  {
    const dataFromCache = await getCache(key);

    if (dataFromCache !== undefined) {
        return dataFromCache;
    }

    if (!refPromises[key]) {
        refPromises[key] = new Promise(async (resolve, reject) => {
            const dataFromDb = await getDataFromDb(key);
            await setCache(key, dataFromDb);
            delete refPromises[key]; // required only if cached value can become "stale"
            resolve(dataFromDb);
        });
    }

    return refPromises[key];
}