--- title: What happens to database listeners when security rules... description: Firebase Realtime Database client SDKs optimistically apply local writes and trigger listeners immediately, before the server confirms the write against... canonical: https://daily.dev/posts/what-happens-to-database-listeners-when-security-rules-reject-an-update--cebdqtzlk twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: What happens to database listeners when security rules reject an update? | daily.dev og:description: Firebase Realtime Database client SDKs optimistically apply local writes and trigger listeners immediately, before the server confirms the write against... og:url: https://daily.dev/posts/what-happens-to-database-listeners-when-security-rules-reject-an-update--cebdqtzlk og:image: https://api.daily.dev/og/posts/ceBDqtzlk.png og:image:alt: What happens to database listeners when security rules reject an update? 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. # What happens to database listeners when security rules reject an update? **[Firebase](https://daily.dev/sources/firebase-blog)** · 10 min read · 0 upvotes · 0 comments ## Summary Firebase Realtime Database client SDKs optimistically apply local writes and trigger listeners immediately, before the server confirms the write against security rules. If a security rule rejects the write, the SDK rolls back by triggering listeners again with the original data, which can cause confusing sequences like a ValueEventListener firing with a new value, then an error, then the original value again, or a ChildEventListener firing onChildAdded followed by onChildRemoved. This optimistic-update behavior keeps apps responsive offline or on poor connections but can surprise developers who expect security rule violations to simply be silently blocked. The post explains this flow step by step and recommends using a CompletionListener or the Task API returned by setValue() to explicitly detect and handle write failures, such as reporting them to Firebase Crash Reporting. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why does my Firebase Realtime Database ValueEventListener fire with a new value even though my security rules should block the write? The Firebase Realtime Database client SDK optimistically assumes writes will succeed and immediately triggers listeners with the new value before contacting the server. If the server then rejects the write due to security rules, it notifies the client, which rolls back by triggering the listener again with the original data, producing a sequence of new-value, error, then original-value callbacks. _Developers debugging optimistic-update quirks in Firebase can find real-world explanations like this on daily.dev._ ### How do I detect if a Firebase Realtime Database setValue() call actually failed due to a security rule violation? Use a CompletionListener passed to an overload of setValue(), or use the Task object returned by setValue() with an OnCompleteListener. Checking task.isSuccessful() after completion reveals whether the write failed, and the exception can be reported to Firebase Crash Reporting to catch programming errors or unexpected rule violations. _daily.dev surfaces practical fixes like this for developers hardening their Firebase write-error handling._ ### What happens to a Firebase ChildEventListener when a push to a write-protected node is rejected? The client SDK immediately fires onChildAdded with the new pushed child object, assuming the write will succeed. After the server rejects the write because of security rules, the SDK calls onChildRemoved with the same object to undo the optimistic add, keeping the app UI consistent with server-confirmed data. _daily.dev helps developers building real-time UIs track these Firebase listener edge cases._ ## Similar posts on daily.dev - [No Rules, No Locks: Firebase Misconfiguration and the Borrowers It Left Behind](https://daily.dev/posts/no-rules-no-locks-firebase-misconfiguration-and-the-borrowers-it-left-behind-dfdzx9pyz) · InfoSec Write-ups · 0 upvotes · 0 comments - [What Firebase’s Docs Don’t Tell You About Remote Config in React Native \(2026\)](https://daily.dev/posts/what-firebase-s-docs-don-t-tell-you-about-remote-config-in-react-native-2026--063rjk39t) · Medium · 0 upvotes · 0 comments - [Insecure Firestore Security Rules & PII Exposure](https://daily.dev/posts/insecure-firestore-security-rules-pii-exposure-2yicfecec) · InfoSec Write-ups · 0 upvotes · 0 comments --- Tags: [#android](https://daily.dev/tags/android), [#backend](https://daily.dev/tags/backend), [#firebase](https://daily.dev/tags/firebase) [View this post on daily.dev](https://daily.dev/posts/what-happens-to-database-listeners-when-security-rules-reject-an-update--cebdqtzlk) ```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":"What happens to database listeners when security rules reject an update?","url":"https://daily.dev/posts/what-happens-to-database-listeners-when-security-rules-reject-an-update--cebdqtzlk","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/what-happens-to-database-listeners-when-security-rules-reject-an-update--cebdqtzlk"},"datePublished":"2026-08-23T12:21:15.299Z","dateModified":"2026-08-23T12:37:42.611Z","description":"Firebase Realtime Database client SDKs optimistically apply local writes and trigger listeners immediately, before the server confirms the write against...","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/what-happens-to-database-listeners-when-security-rules-reject-an-update--cebdqtzlk","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"android,backend,firebase","timeRequired":"PT10M"} {"@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":"What happens to database listeners when security rules reject an update?"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/what-happens-to-database-listeners-when-security-rules-reject-an-update--cebdqtzlk#faq","mainEntity":[{"@type":"Question","name":"Why does my Firebase Realtime Database ValueEventListener fire with a new value even though my security rules should block the write?","acceptedAnswer":{"@type":"Answer","text":"The Firebase Realtime Database client SDK optimistically assumes writes will succeed and immediately triggers listeners with the new value before contacting the server. If the server then rejects the write due to security rules, it notifies the client, which rolls back by triggering the listener again with the original data, producing a sequence of new-value, error, then original-value callbacks. Developers debugging optimistic-update quirks in Firebase can find real-world explanations like this on daily.dev."}},{"@type":"Question","name":"How do I detect if a Firebase Realtime Database setValue() call actually failed due to a security rule violation?","acceptedAnswer":{"@type":"Answer","text":"Use a CompletionListener passed to an overload of setValue(), or use the Task object returned by setValue() with an OnCompleteListener. Checking task.isSuccessful() after completion reveals whether the write failed, and the exception can be reported to Firebase Crash Reporting to catch programming errors or unexpected rule violations. daily.dev surfaces practical fixes like this for developers hardening their Firebase write-error handling."}},{"@type":"Question","name":"What happens to a Firebase ChildEventListener when a push to a write-protected node is rejected?","acceptedAnswer":{"@type":"Answer","text":"The client SDK immediately fires onChildAdded with the new pushed child object, assuming the write will succeed. After the server rejects the write because of security rules, the SDK calls onChildRemoved with the same object to undo the optimistic add, keeping the app UI consistent with server-confirmed data. daily.dev helps developers building real-time UIs track these Firebase listener edge cases."}}]} ```