--- title: Client-side fan-out for data consistency | daily.dev description: Multi-path updates, introduced in a Firebase SDK release, enable a technique called client-side fan-out where clients build a single object keyed by deep paths... canonical: https://daily.dev/posts/client-side-fan-out-for-data-consistency-quilwbvgu twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Client-side fan-out for data consistency | daily.dev og:description: Multi-path updates, introduced in a Firebase SDK release, enable a technique called client-side fan-out where clients build a single object keyed by deep paths... og:url: https://daily.dev/posts/client-side-fan-out-for-data-consistency-quilwbvgu og:image: https://api.daily.dev/og/posts/quIlWbVgU.png og:image:alt: Client-side fan-out for data consistency og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Client-side fan-out for data consistency **[Firebase](https://daily.dev/sources/firebase-blog)** · 7 min read · 0 upvotes · 0 comments ## Summary Multi-path updates, introduced in a Firebase SDK release, enable a technique called client-side fan-out where clients build a single object keyed by deep paths and send it in one atomic update. This solves the consistency problem in fanned-out (denormalized) data structures, like duplicating a post across every follower's timeline, without needing complicated rollback logic if a write fails partway through. Code examples are shown for JavaScript, Swift, and Java/Android. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do I use Firebase multi-path updates to keep fanned-out data consistent? Multi-path updates let a client build a single fan-out object whose keys are deep paths, then send it with one call to update(), making the write atomic across every location. For example, updating a user record in /users/1, /usersWhoAreCool/1, and /usersToGiveFreeStuffTo/1 in one call either fully succeeds or fully fails, avoiding partial writes. _daily.dev surfaces practical Firebase patterns like this for developers building real-time data models._ ### Why does denormalizing data in a Firebase Realtime Database cause consistency problems when editing a post? Before multi-path updates, editing a post required querying every location where it was duplicated (like each follower's timeline) and updating them individually, which could fail partway through on a lost connection and leave data in an incomplete state requiring a complicated rollback. Client-side fan-out solves this by combining all those writes into one atomic multi-path update. _Developers weighing denormalization trade-offs can find real-time database patterns like this on daily.dev._ ## Similar posts on daily.dev - [When Notifications Became Data Trucks: A Real-World Crash Story from Firebase FCM](https://daily.dev/posts/when-notifications-became-data-trucks-a-real-world-crash-story-from-firebase-fcm-nh9ixqylv) · ProAndroidDev · 1 upvotes · 0 comments - [Android Data Synchronization: Beyond Room & WorkManager](https://daily.dev/posts/android-data-synchronization-beyond-room-workmanager-ntg9szb81) · Medium · 0 upvotes · 0 comments - [Cloud Bits: Breaking the Double Write – A Guide to Distributed Data Consistency – Distributed Computing Musings](https://daily.dev/posts/cloud-bits-breaking-the-double-write-a-guide-to-distributed-data-consistency-distributed-comput-i2embckph) · Distributed Computing Musings · 0 upvotes · 0 comments - [How Firestore Structures Data and How to Perform CRUD Operations With It](https://daily.dev/posts/how-firestore-structures-data-and-how-to-perform-crud-operations-with-it-odioykply) · freeCodeCamp · 1 upvotes · 0 comments --- Tags: [#javascript](https://daily.dev/tags/javascript), [#backend](https://daily.dev/tags/backend), [#firebase](https://daily.dev/tags/firebase), [#nosql](https://daily.dev/tags/nosql) [View this post on daily.dev](https://daily.dev/posts/client-side-fan-out-for-data-consistency-quilwbvgu) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Client-side fan-out for data consistency","url":"https://daily.dev/posts/client-side-fan-out-for-data-consistency-quilwbvgu","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/client-side-fan-out-for-data-consistency-quilwbvgu"},"datePublished":"2026-08-23T12:20:23.897Z","dateModified":"2026-08-24T06:58:55.822Z","description":"Multi-path updates, introduced in a Firebase SDK release, enable a technique called client-side fan-out where clients build a single object keyed by deep paths...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/7ed721de96163685d26ab7e314be3ebc?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/7ed721de96163685d26ab7e314be3ebc?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Firebase","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Firebase","logo":"https://media.daily.dev/image/upload/s--i395oqZH--/f_auto,q_auto/v1787487448/logos/firebase-blog?_a=BAMAMicg0","url":"https://daily.dev/sources/firebase-blog"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/client-side-fan-out-for-data-consistency-quilwbvgu","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"javascript,backend,firebase,nosql","timeRequired":"PT7M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Firebase","item":"https://daily.dev/sources/firebase-blog"},{"@type":"ListItem","position":3,"name":"Client-side fan-out for data consistency"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/client-side-fan-out-for-data-consistency-quilwbvgu#faq","mainEntity":[{"@type":"Question","name":"How do I use Firebase multi-path updates to keep fanned-out data consistent?","acceptedAnswer":{"@type":"Answer","text":"Multi-path updates let a client build a single fan-out object whose keys are deep paths, then send it with one call to update(), making the write atomic across every location. 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