In this article by Manoj Waikar, author of the book Data-oriented Development with AngularJS, we will learn a brief description about various types of persistence mechanisms, local versus hosted databases, what Firebase is, why to use it, and different use cases where Firebase can be useful.

(For more resources related to this topic, see here.)

We can write web applications by using the frameworks of our choice—be it server-side MVC frameworks, client-side MVC frameworks, or some combination of these. We can also use a persistence store (a database) of our choice—be it an RDBMS or a more modern NoSQL store. However, making our applications real time (meaning, if you are viewing a page and data related to that page gets updated, then the page should be updated or at least you should get a notification to refresh the page) is not a trivial task and we have to start thinking about push notifications and what not. This does not happen with Firebase.

Persistence

One of the very early decisions a developer or a team has to make when building any production-quality application is the choice of a persistent storage mechanism. Until a few years ago, this choice, more often than not, boiled down to a relational database such as Oracle, SQL Server, or PostgreSQL. However, the rise of NoSQL solutions such as MongoDB (http://www.mongodb.org/) and CouchDB (http://couchdb.apache.org/)—document-oriented databases or Redis (http://redis.io/), Riak (http://basho.com/riak/), keyvalue stores, Neo4j (http://www.neo4j.org/), and a graph database—has widened the choice for us. Please check the Wikipedia page on NoSQL (http://en.wikipedia.org/wiki/NoSQL) solutions for a detailed list of various NoSQL solutions including their classification and performance characteristics.

There is one more buzzword that everyone must have already heard of, Cloud, the short form for cloud computing. Cloud computing briefly means that shared resources (or software) are provided to consumers on a paid/free basis over a network (typically, the Internet). So, we now have the luxury of choosing our preferred RDBMS or NoSQL database as a hosted solution. Consequently, we have one more choice to make—whether to install the database locally (on our own machine or inside the corporate network) or use a hosted solution (in the cloud).

As with everything else, there are pros and cons to each of the approaches. The pros of a local database are fast access and one-time buying cost (if it's not an open source database), and the cons include the initial setup time. If you have to evaluate some another database, then you'll have to install the other database as well. The pros of a hosted solution are ease of use and minimal initial setup time, and the cons are the need for a reliable Internet connection, cost (again, if it's not a free option), and so on.

Considering the preceding pros and cons, it's a safe bet to use a hosted solution when you are still evaluating different databases and only decide later between a local or a hosted solution, when you've finally zeroed in on your database of choice.

What is Firebase?

So, where does Firebase fit into all of this? Firebase is a NoSQL database that stores data as simple JSON documents. We can, therefore, compare it to other document-oriented databases such as CouchDB (which also stores data as JSON) or MongoDB (which stores data in the BSON, which stands for binary JSON, format).

Although Firebase is a database with a RESTful API, it's also a real-time database, which means that the data is synchronized between different clients and with the backend server almost instantaneously. This implies that if the underlying data is changed by one of the clients, it gets streamed in real time to every connected client; hence, all the other clients automatically get updates with the newest set of data (without anyone having to refresh these clients manually).

So, to summarize, Firebase is an API and a cloud service that gives us a real-time and scalable (NoSQL) backend. It has libraries for most server-side languages/frameworks such as Node.js, Java, Python, PHP, Ruby, and Clojure. It has official libraries for Node.js and Java and unofficial third-party libraries for Python, Ruby, and PHP. It also has libraries for most of the leading client-side frameworks such as AngularJS, Backbone, Ember, React, and mobile platforms such as iOS and Android.

Firebase – Benefits and why to use?

Firebase offers us the following benefits:

It is a cloud service (a hosted solution), so there isn't any setup involved.
Data is stored as native JSON, so what you store is what you see (on the frontend, fetched through a REST API)—WYSIWYS.
Data is safe because Firebase requires 2048-bit SSL encryption for all data transfers.
Data is replicated and backed-up to multiple secure locations, so there are minimal chances of data loss.
When data changes, apps update instantly across devices.
Our apps can work offline—as soon as we get connectivity, the data is synchronized instantly.
Firebase gives us lightning fast data synchronization. So, combined with AngularJS, it gives us three-way data binding between HTML, JavaScript, and our backend (data).

With two-way data binding, whenever our (JavaScript) model changes, the view (HTML) updates itself and vice versa. But, with three-way data binding, even when the data in our database changes, our JavaScript model gets updated, and consequently, the view gets updated as well.

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Last but not the least, it has libraries for the most popular server-side languages/frameworks (such as Node.js, Ruby, Java, and Python) as well as the popular client-side frameworks (such as Backbone, Ember, and React), including AngularJS. The Firebase binding for AngularJS is called AngularFire (https://www.firebase.com/docs/web/libraries/angular/).

Firebase use cases

Now that you've read how Firebase makes it easy to write applications that update in real time, you might still be wondering what kinds of applications are most suited for use with Firebase. Because, as often happens in the enterprise world, either you are not at liberty to choose all the components of your stack or you might have an existing application and you just have to add some new features to it. So, let's study the three main scenarios where Firebase can be a good fit for your needs.

Apps with Firebase as the only backend

This scenario is feasible if:

You are writing a brand-new application or rewriting an existing one from scratch
You don't have to integrate with legacy systems or other third-party services
Your app doesn't need to do heavy data processing or it doesn't have complex user authentication requirements

In such scenarios, Firebase is the only backend store you'll need and all dynamic content and user data can be stored and retrieved from it.

Existing apps with some features powered by Firebase

This scenario is feasible if you already have a site and want to add some real-time capabilities to it without touching other parts of the system. For example, you have a working website and just want to add chat capabilities, or maybe, you want to add a comment feed that updates in real time or you have to show some real-time notifications to your users.

In this case, the clients can connect to your existing server (for existing features) and they can connect to Firebase for the newly added real-time capabilities. So, you can use Firebase together with the existing server.

Both client and server code powered by Firebase

In some use cases, there might be computationally intensive code that can't be run on the client. In situations like these, Firebase can act as an intermediary between the server and your clients. So, the server talks to the clients by manipulating data in Firebase. The server can connect to Firebase using either the Node.js library (for Node.js-based server-side applications) or through the REST API (for other server-side languages). Similarly, the server can listen to the data changes made by the clients and can respond appropriately. For example, the client can place tasks in a queue that the server will process later. One or more servers can then pick these tasks from the queue and do the required processing (as per their availability) and then place the results back in Firebase so that the clients can read them.

Firebase is the API for your product

You might not have realized by now (but you will once you see some examples) that as soon as we start saving data in Firebase, the REST API keeps building side-by-side for free because of the way data is stored as a JSON tree and is associated on different URLs. Think for a moment if you had a relational database as your persistence store; you would then need to specially write REST APIs (which are obviously preferable to old RPC-style web services) by using the framework available for your programming language to let external teams or customers get access to data. Then, if you wanted to support different platforms, you would need to provide libraries for all those platforms whereas Firebase already provides real-time SDKs for JavaScript, Objective-C, and Java.

So, Firebase is not just a real-time persistence store, but it doubles up as an API layer too.