mongoose helper for heavy lifting of un-indexed collections

Balrok What?

Balrok is a mongoose helper for heavy lifting of un-indexed collections.


Large MongoDB collections work very well, if you have enough RAM and the fields you are filtering for are indexed. However that is very often not the case and that might result in a lot of frustration, besides frying your cluster or getting no results for minutes of query time.

Balrok helps you very easily to run your aggregations and filters using your client in a safe and efficient manner. It ships with a distributed query processing stack, as well as its own cache collection for your query result.

How ?

You can simply spin up your mongoose setup as you are used to, as soon as you are connected to MongoDB you create a new instance of Balrok and call initto prepare it. When you are ready to go, you can pass your large un-indexed queries straight to your Balrok instance's resolvemethod. Balrock will stream your documents from batch find queries and call your document operation function on every document, the results are stored in the cache collection and shared with all instances. If another instance of your code is already running the same query, balrok will await the results of that instances process before returning them.

const balrok = new Balrok({
        cacheCollectionName: "balrok_cache_test",
        cacheTimeMs: 60 * 1000 * 5,
        maxParallelProcesses: 5,

    await balrok.init();

    const query = { /* to resolve fast queries, these should only contain indexed fields */ };

    const documentOperation = (doc: any) => {
        /* instead the actually filtering is done in the streamed document operation */
        return doc.firstName === "Chris";

    const resolveOptions = {
        options: {}, // mongoose find options
        batchSize: 12, // default is 512
        order: -1, // default is -1
        timeoutMs: 5000, // default is 3 minutes
        dontAwait: true, // default is false
        noCache: false, // default is false
        limit: 2, // default is null (which will not apply any limit)

    const results = await balrok.filter(testModel, query, "aQueryName", documentOperation, resolveOptions));

    /* Other available operations:
        - await balrok.filter()
        - await balrok.reduce()
        - await
        - await balrok.resolve() // combines filter and map

A full running sample (with mongoose connection) can be found here.






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