eventing-function.js

// Eventing Function skeleton
// Bindings required (configure in Eventing UI or REST API):
//   src  — source collection (read-only or read+write)
//   dst  — destination collection (read+write)
//
// Deploy settings:
//   Feed boundary: "From now" (new mutations only) or "Everything" (backfill + new)
//   Workers: 1–64 (scale with mutation rate)

function OnUpdate(doc, meta) {
    // Guard: only process relevant document types
    if (doc.type !== "REPLACE_TYPE") return;

    // Guard: skip already-processed documents to prevent double mutations
    if (doc.processed) return;

    // --- Your logic here ---

    // Write to destination collection
    dst[meta.id] = Object.assign({}, doc, {
        processed: true,
        processedAt: new Date().toISOString()
    });
}

function OnDelete(meta, options) {
    // options.is_expiry — true if deleted by TTL expiry
    if (options.is_expiry) {
        log("Document expired:", meta.id);
    }

    // Cascade delete to destination
    delete dst[meta.id];
}