Ever waited to order or pay in a restaurant with a waiter holding his ordering device high up into the air, searching for connectivity, or wanted to use an app These moments show why data synchronization is essential. With more and more services relying on the availability of on-device apps and the IoT market projected to hit $1.1 trillion by 2026, choosing the right sync solution – offline or online – is more crucial than ever. In this blog, we discuss their differences and highlight common Data Sync alternatives.
What is Data Sync?
Data synchronization (Sync) aligns data between two or more devices to maintain consistency over time. It is an essential component in applications ranging from IoT and mobile apps to cloud computing. Challenges in data synchronization include asynchrony, conflicts, and managing data across flaky networks.
Data Sync vs. Data Replication
Data Synchronization is often confused with Data Replication. Nevertheless, they serve different purposes:
- Data Replication: A unidirectional process (works in one direction only) that duplicates data across storage locations to ensure availability and prevent loss. It is simple but limited in its application, and efficiency, and lacks conflict management.
- Data Synchronization: A bidirectional process that harmonizes all or a subset of data between two or more devices. It ensures consistency across devices and entails conflict resolution. It is inherently more complex but also more flexible.
Online vs Offline Solutions: Why Offline Sync Matters
Online-only synchronization solutions rely entirely on cloud infrastructure, requiring a stable internet connection to function. While these tools offer simplicity and scalability, their dependency on constant cloud connectivity brings limitations: Online Data Sync solutions cannot guarantee response rates and their speed varies depending on the network. They do not work when offline or in on-premise settings. Using an Online Sync solution often entails sharing the data and might not comply with data privacy requirements. So, do read the terms and conditions.
Offline-first solutions focus on local data storage and processing, ensuring the app remains fully functional even without an internet connection. When a network is available, the app synchronizes seamlessly with a server, the cloud, or other devices as needed. These solutions are ideal for on-premise scenarios with unreliable or no internet access, mission-critical applications that must always operate, real-time and high-performance use cases, as well as situations requiring high data privacy and data security compliance.
A less discussed, but in our view also relevant point, is sustainability. While there might be exceptions depending on the use case, for most applications offline-first solutions are more resourceful and therefore more sustainable. If CO2 footprint or battery usage is of concern to you, you might want to look into offline-first Data Sync alternatives.
Now, let’s have a look at current options:
Data Sync Alternatives
| Solution | Type | Offline Support | Self-hosted Sync | Decentralized Sync | Open-Source Component | Other Considerations |
| Firebase | Online | ✅ (local cache, syncs when online) | ❌ | ❌ | ❌ | Tied to Google Cloud, requires internet connectivity |
| Supabase | Online | Limited | ✅ | ❌ | ✅ | Relies on Supabase cloud unless self-hosted |
| ObjectBox | Offline-first | ✅ | ✅ | In development | ✅ | Fully offline-first, supports on-premise/cloud |
| Couchbase (Light + Couchbase Sync) | Online | ✅ (Couchbase Light) | ✅ | ❌ | ✅ | Tied to Couchbase servers, can quickly get very expensive |
| MongoDB Realm + Atlas Device Sync | Offline-first | ✅ | Cloud-based sync only | ❌ | ✅ | Deprecated (in Sept 2025) |
While SQLite does not offer a sync solution out-of-the-box, various vendors have built something on top, or integrated with SQLite giving them offline persistence.
Key Considerations for Choosing a Data Sync Solution
When selecting a synchronization solution, consider:
- Connectivity Requirements: Will the application function in offline environments; how will it work with flaky network conditions; how is the user experience when there is intermittent connectivity?
- Data Privacy & Security: How critical is it to ensure sensitive data remains local? Data compliance? How important is it that data is not breached?
- Scalability and Performance: What are the expected data loads and network constraints? How important is speed for the users? Is there any need to guarantee QoS parameters? How much will the cloud and networking costs be?
- Conflict Resolution: How does the solution handle data conflicts?
- Delta Sync: Does the solution always synchronize all data or only changes (data delta)? Can a subset of data be synchronized? How efficient is the Sync protocol (affecting costs and speed)?
The Shift Towards Edge Computing
The trend toward Edge Computing highlights the growing preference for offline-first solutions. By processing and storing data closer to its source, Edge Computing reduces cloud dependency, enhances privacy, and improves efficiency. Data synchronization plays an important role in this shift, ensuring seamless operation across decentralized networks.
Offline and online synchronization solutions each have their merits, but the rise of edge computing and data privacy concerns has propelled offline-first solutions to the forefront. Developers must assess their application’s unique requirements to select the most appropriate synchronization method. As the industry evolves, hybrid and offline-first solutions are going to dominate, offering the best balance of functionality, privacy, and performance.