Today, mobile apps are the face of any service or business online. One of the biggest challenges for a mobile app developer is to choose the right database to support the app.
The app can require a database for multiple reasons such as, to store the following information
- user authentication information,
- transactions carried out by a user,
- listing and updating inventory,
- offline state when out of network
The database for an app is selected based on the purpose of building the app. This blog aims to aid the app developer in choosing the correct database based on some specific criteria. In doing so, we have listed five popular databases for mobile apps in 2022, with their benefits and limitations to help an app developer make an informed decision.
Choosing the right database for your mobile application
Here are some of the vital pointers to look out for while selecting a mobile database
Need for using the local store of the device
- If the app does not have a server requirement
- If the app needs to function everywhere, even when the network is off
- If the app is a part of a distributed landscape and needs to store data pertaining to itself
- If the load is to be shared with the app’s local store and a central database
Cross-platform support
- If the app has to be built across ios or android or all platforms
- If the app is hybrid
Data Model
- A relational database would be the right choice if the schema is well defined and requires consistency, more writes and complex querying.
- For a continuously evolving app, a NoSQL database makes sense.
Synchronization support
If the application needs to sync with peers or a central database, it is best to go with a database that provides a sync feature such as Realm or Couchbase Lite.
Type of database
One would need to go in for a structured RDBMS or an unstructured NoSQL database based on many factors. These factors are:
Schema evolution – A startup or, broadly, an internet company requires quicker Agile cycles of product changes and, therefore, a flexible data schema. Choosing an RDBMS would mean expensive Alter statements and time-consuming data migration. It would need a full-time DBA, whereas a NoSQL database is built for this kind of flexibility.
Fixed data structure – An RDBMS would make sense over a NoSQL. If the app requires a large volume of data reads instead of writes, a NoSQL could be considered.
Storing large volumes of data – Again, a NoSQL database comes with sharding facilities out of the box. Large data storage can be achieved manually with RDBMS, but they are classically built for vertical scalability.
Transactions – While a few NoSQL databases ensure consistency, the more extensive set provides availability over real-time consistency. This is where an RDBMS works best.
Analytics – RDBMS works best for complex analytical queries.
Caching – A good datastore for managing user sessions would be a key value of the NoSQL database.
Social network operations – A graph-based NoSQL database would work best.
Cost – Legacy RDBMS requires expensive hardware and annual licenses. Cloud-based databases could run up a bill based on the kind of querying or updates required.
SAAS-based app – Ideally, the database would be on the cloud. Banking apps require high security and, therefore, might be on-premise.
App or platform’s technology– Choice of the database can also be governed by the type of technology used. Mongo is popularly used with NodeJS, Postgresql with Python, and Mysql with Java. It is not a deciding factor but based on the skill pool.
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Five popular databases for mobile apps development
Here are five popular databases available in the market today to choose from for mobile app development –
SQLite
SQLite is a lightweight SQL database engine following the principles of RDBMS. It is built into every mobile device.
Benefits
- Lightweight – As is needed in a mobile device.
- Cost – Free and zero configuration.
- Performance – Very fast when compared to writing the file system
- Reliable – It updates content continuously so that data is not lost due to power failure.
- Platform support – It provides cross-platform support like iOS, Android, Windows, and Mac.
Limitations
- Not scalable and not suitable for large data storage.
- It does not support concurrent transactions
- Lacks built-in data security features
- It’s not a full-fledged RDBMS like MYSQL lacking fine-grained access control, support for joins, a GUI for ease of use.
REALM
Realm is an open-source object database for the mobile app by Mongo. It runs on the client device and is available for both native and cross framework apps.
Benefits
- Object-oriented data model and therefore easy for developers to understand and work with
- Realm is offline first. Data is read and written to the device. If server-side sync is required, then Realm sync can be enabled. This synchronizes data with the Mongo realm using a background thread on the server-side.
- Realm enables fast querying with its lazy loading and a zero-copy architecture. All Realm objects are live objects that reflect the most current data and can be subscribed to for changes.
- Realm Triggers automatically execute a function at a scheduled time or when an event occurs, such as a change to a database or a call to an HTTP endpoint.
- Data can be encrypted in-flight and at rest, keeping even the most sensitive data secure. Realm has built-in user management that can be integrated with third-party authentication providers such as Google and Facebook. Rules can be defined for controlling data access.
- Realm is open source. It is distributed under the Apache 2.0 license and backed by MongoDB.
- It is cross-platform and can be used with Swift, Objective-C, Java, Kotlin, C#, and JavaScript.
Limitations
- Realm affects the apk size.
- Realm requires a schema to model the data and relationships. Therefore migrating to Realm DB comes at a cost.
- Realm objects can be modified only within a transaction, making it cumbersome and requiring disciplined use of the database.
- Auto-increment of primary keys does not come out of the box. It has to be taken care of programmatically.
- Closing Realm connection after use should be followed strictly to prevent memory leaks as the garbage collector does not know how to work with Realm objects.
- Realm Sync does not currently support sharded MongoDB Atlas clusters. However, a sharded cluster can be accessed as data sources through functions and MongoDB Data Access.
- Syncing to Mongo at the back-end comes at a cost.
Couchbase Lite
Couchbase Lite is another NoSQL-based mobile database for the offline-first experience.
Benefits
- Couchbase mobile supports both native and cross-platform frameworks
- Couchbase provides an end to end data management solution referred to as Couchbase Mobile with –
- Couchbase Lite as the embedded store for the app,
- Sync gateway synchronizes data over the web using constructs such as REST APIs, batch updates, events.
- Couchbase Server, which can serve as the full-fledged central back-end store
- Data security is provided across the entire stack, including user authentication, role-based access, and data encryption at rest and in motion.
- Data can be stored as JSON documents or blobs. Therefore storing multimedia, IoT, or regular data of applications can be stored easily.
- Since Couchbase Mobile allows JSON documents, it is schemaless, and therefore migration comes at zero cost.
- It is lightweight, between 1-5MB
Limitations
- Arbitrary querying is not possible. It has to be done only through views which are indexes internally and therefore extremely fast. But views don’t work well with complex queries that might require more than one view to resolve.
- CouchDB does not work well with full-text searches.
- Doesn’t have an out-of-the-box object mapper. This needs to be coded in by the developer.
- Couchbase is shipped with a small instance of Memcache to handle the in-memory cache, which hogs memory for many documents and degrades performance.
- Enterprise support is expensive.
Cloud Firestore
Cloud Firestore is a NoSQL database provided by Google as a part of its mobile application development platform, Firebase. While the data storage is online-first, it does support offline data persistence. This feature, when enabled, caches a copy of the data to write/read when the device is offline. It syncs back to the server when the device is back on the network. The benefit of choosing Firestore is that it’s a part of Firebase, which provides a host of services to enable the app developer to use ready-made features such as user authentication to analytics with minimal customization and no servers to manage.
Benefits
- Data is stored in the form of documents that can be queried easily
- Provides automatic sync of data between devices offline data storage and notifies the app on data changes.
- Firestore provides strong authentication and authorization based on user identification and other criteria. It also integrates with Firebase authentication, which supports user/password and third-party authentication integration such as Google, Twitter, and Facebook.
- Very high performance.
- Backed by Google’s cloud infrastructure, Firestore scales easily.
- It provides excellent cross-platform support.
Limitations
- It can become expensive.
- Complex queries and full text-based search are not handled well in most NoSQL databases.
- Offline query performance is slow.
- Document size is limited to 1 MB
- Writes are expensive and limited to 1 write/second. It works best for read-intensive apps.
Oracle Berkeley DB
Oracle Berkeley DB is an open-source embeddable database allowing developers the choice of SQL, Key/Value, XML/XQuery, or Java Object storage for their data model. It is available in three versions -Berkeley DB, Berkeley DB Java Edition, and Berkeley DB XML
Benefits
- Provides a choice of schema between NoSQL and RDBMS
- Berkley DB provides a SQL API that is fully compatible with SQLite. This gives the developer an option to migrate to Berkeley or use SQLite under the hood.
- Provides cross-platform support
- Rich querying, indexing, and transactional support provide a tremendous full-text search for the SQL implementation.
Limitations
- Heavier footprint compared to the NoSQL option.
- It allows an open-source license as long as the developer’s code is freely redistributable. Otherwise, one has to go for the commercial license.
- Support under an open-source license is not great.
Ultimately, selecting an ideal database for your mobile application depends on its requirements and feasibility for the application.
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