--- title: "What conflict resolution strategies would you use during online sync?" description: "What conflict resolution strategies would you use during online sync?" author: "ICSM Computer" published: 2025-07-10 updated: 2025-07-10 canonical: https://www.mindstick.com/interview/34330/what-conflict-resolution-strategies-would-you-use-during-online-sync category: "IndexedDB" tags: ["database", "indexeddb"] reading_time: 5 minutes --- # What conflict resolution strategies would you use during online sync? ### What conflict resolution strategies would you use during online sync (e.g., server-wins vs client-wins)? When implementing **conflict resolution strategies during online sync**, you typically choose based on the nature of your application, the data importance, and user expectations. Here are the most common strategies, with pros/cons and when to use them: ### 1. Server-Wins (Last-Write-Wins by server) - **Description**: If there's a conflict, the server version overwrites the client's. - **Use When**: - The server holds the authoritative source of truth. - Changes on the client are usually not critical or are derived from server data. - **Example**: Stock market apps, CMS dashboards. - **Pros**: - Simple and centralized. - **Cons**: - Client-side edits may be lost silently. ### 2. Client-Wins - **Description**: The client version is pushed and overrides the server’s version. - **Use When**: - Offline-first apps where client changes are prioritized (e.g., personal notes, task apps). - **Example**: To-do apps like Google Keep. - **Pros**: - Feels responsive; user retains control. - **Cons**: - Can overwrite critical server data accidentally. ### 3. Last-Write-Wins (Timestamp-Based) - **Description**: Whichever update (client or server) is newest (based on timestamp) wins. - **Use When**: - You trust both sides and track update times. - **Pros**: - Automatic and simple. - **Cons**: - Prone to time drift issues if client clock is incorrect. ### 4. Manual Merge (User-Assisted) - **Description**: If conflict occurs, show both versions and let user choose or merge. - **Use When**: - Data is sensitive or collaborative. - **Example**: Document editing apps, CRM systems. - **Pros**: - No accidental data loss. - **Cons**: - Requires UI for conflict handling, and user effort. ### 5. Field-Level Merge - **Description**: Only update specific fields that changed; merge non-conflicting fields. - **Use When**: - Objects contain multiple independent fields (e.g., profile form: name, email, phone). - **Pros**: - Minimizes conflicts. - **Cons**: - More complex implementation. ### 6. Operational Transformation / CRDTs - **Description**: Merge changes at the operation level (like in collaborative editors). - **Use When**: - Real-time multi-user editing. - **Example**: Google Docs, collaborative whiteboards. - **Pros**: - Enables concurrent edits. - **Cons**: - Complex to build and maintain. ### Recommended Hybrid Approach In many real-world apps, a **hybrid approach** is best: - Use **timestamp-based sync** for simple objects. - Use **field-level merges** for form-based records. - Fall back to **manual merge** when high-value data is at risk. - Optionally allow configurable resolution policies (e.g., “Always prefer my device’s data”). ## Answers ### Answer by ICSM Computer ### What conflict resolution strategies would you use during online sync (e.g., server-wins vs client-wins)? When implementing **conflict resolution strategies during online sync**, you typically choose based on the nature of your application, the data importance, and user expectations. Here are the most common strategies, with pros/cons and when to use them: ### 1. Server-Wins (Last-Write-Wins by server) - **Description**: If there's a conflict, the server version overwrites the client's. - **Use When**: - The server holds the authoritative source of truth. - Changes on the client are usually not critical or are derived from server data. - **Example**: Stock market apps, CMS dashboards. - **Pros**: - Simple and centralized. - **Cons**: - Client-side edits may be lost silently. ### 2. Client-Wins - **Description**: The client version is pushed and overrides the server’s version. - **Use When**: - Offline-first apps where client changes are prioritized (e.g., personal notes, task apps). - **Example**: To-do apps like Google Keep. - **Pros**: - Feels responsive; user retains control. - **Cons**: - Can overwrite critical server data accidentally. ### 3. Last-Write-Wins (Timestamp-Based) - **Description**: Whichever update (client or server) is newest (based on timestamp) wins. - **Use When**: - You trust both sides and track update times. - **Pros**: - Automatic and simple. - **Cons**: - Prone to time drift issues if client clock is incorrect. ### 4. Manual Merge (User-Assisted) - **Description**: If conflict occurs, show both versions and let user choose or merge. - **Use When**: - Data is sensitive or collaborative. - **Example**: Document editing apps, CRM systems. - **Pros**: - No accidental data loss. - **Cons**: - Requires UI for conflict handling, and user effort. ### 5. Field-Level Merge - **Description**: Only update specific fields that changed; merge non-conflicting fields. - **Use When**: - Objects contain multiple independent fields (e.g., profile form: name, email, phone). - **Pros**: - Minimizes conflicts. - **Cons**: - More complex implementation. ### 6. Operational Transformation / CRDTs - **Description**: Merge changes at the operation level (like in collaborative editors). - **Use When**: - Real-time multi-user editing. - **Example**: Google Docs, collaborative whiteboards. - **Pros**: - Enables concurrent edits. - **Cons**: - Complex to build and maintain. ### Recommended Hybrid Approach In many real-world apps, a **hybrid approach** is best: - Use **timestamp-based sync** for simple objects. - Use **field-level merges** for form-based records. - Fall back to **manual merge** when high-value data is at risk. - Optionally allow configurable resolution policies (e.g., “Always prefer my device’s data”). --- Original Source: https://www.mindstick.com/interview/34330/what-conflict-resolution-strategies-would-you-use-during-online-sync Copyright © MindStick Software Pvt. Ltd. This Markdown version is provided for developers, AI systems, and offline reading.