Offline First Database Comparison

In this project I have implemented the exact same chat application with different database technologies. You can use it to compare metrics and learn about the differences. The chat app is a web based angular application, with functionality similar to Whatsapp Web.

Implemented Databases:

• AWS Amplify Datastore
• Firebase Firestore
• PouchDB with IndexedDB adapter & CouchDB replication
• RxDB PouchDB with PouchDB Storage & GraphQL replication
• RxDB LokiJS with LokiJS Storage & GraphQL replication
• RxDB Dexie.js with Dexie.js Storage & GraphQL replication
• WatermelonDB with LokiJS adapter (no backend sync atm)

Metrics

All metrics are measured automatically via code in a browser tests (chrome:headless). The results heavily depend on the developers device. You should compare the values relative to another and not as absolute values. Also you might want to create new metrics that better represent how you would use the respective database.

You can reproduce these values by running sh measure-metrics.sh in the root folder.

Metric \ Project	aws	firebase	pouchdb	rxdb-dexie	rxdb-lokijs	rxdb-pouchdb	watermelondb
First angular component render	268ms	322ms	185ms	290ms	211ms	200ms	218ms
Page load time	385ms	217ms	261ms	392ms	293ms	282ms	306ms
First full render	589ms	1556ms	1027ms	953ms	647ms	1095ms	351ms
Insert one message	35ms	392ms	27ms	53ms	17ms	28ms	7ms
Inserting 20 messages one after another	756ms	7199ms	304ms	520ms	253ms	318ms	28ms
Inserting 20 messages in parallel	192ms	5893ms	108ms	465ms	180ms	312ms	205ms
Message insert to message list change	49ms	35ms	146ms	39ms	15ms	22ms	4ms
User change to message list change	20ms	131ms	132ms	75ms	3ms	147ms	4ms
Message search query time	658ms	341ms	230ms	102ms	26ms	60ms	35ms
First full render with many messages	589ms	1584ms	1492ms	954ms	558ms	1575ms	323ms
Storage usage	199kb	2989kb	1180kb	701kb	1271kb	1035kb	1036kb
Bundle size, plain JavaScript	1589kb	912kb	801kb	1078kb	1021kb	1039kb	852kb
Bundle size, minified+gzip	367kb	223kb	192kb	276kb	250kb	265kb	199kb

Metrics Explanation

• Page load time: How long does it take to download and parse the JavaScript bundle.
• First angular component render: How long does it take for the first angular component to be rendered.
• First full render: How long does it take until all relevant data is displayed for the first time.
• Insert one message: How long does it take to insert a single message.
• Inserting 20 messages one after another: How long does it take to insert 20 messages in serial.
• Inserting 20 messages in parallel: How long does it take to insert 20 messages in parallel.
• Message insert to message list change: How long does it take until a new message is rendered to the dom.
• User change to message list change: How long does it take from changing the user to the displaying of the new messages list.
• Message search query time: How long does it take to search for a given message by regex/like-operator.
• First full render with many messages: Time to first full render when many messages exist.
• Storage usage: Size of the stored IndexedDB database after inserting the full test dataset.
• Bundle size, plain JavaScript: The full JavaScript bundle size, without minification or gzip.
• Bundle size, minified+gzip: The full JavaScript bundle size after minification and gzip compression.

Investigations

Why is LokiJS so much faster?

WatermelonDB and the RxDB-LokiJS project use the LokiJS database as storage, which is an in memory database that regularly persists the data to IndexedDB either on interval, or when the browser tab is closed. By doing so, less slow IndexedDB transaction are used. Keeping and processing the data in memory has the benefit of being much faster, but it also has its downsides:

• Initial page load is much slower when much data is already stored in the database, because all data must be loaded before any database operation can be done.
• All data must fit into memory.
• Data can be lost when the JavaScript process is killed ungracefully like when the browser crashes or the power of the PC is terminated.
• There is no multi-tab-support with plain LokiJS. The data is not shared between multiple browser tabs of the same origin. RxDB handles that by adding its own multi tab handling via the BroadcastChannel module.

Why is Firebase so slow on first render?

On the first page load, Firebase ensures that the local data is equal to the server side state. This means that the client has to be online at application startup which is the reason why Firebase is not completely offline first. To ensure the equalness of client side data, Firebase has to perform several requests to the backend, before the database will respond to queries. This makes the inital page load slow, and it becomes even more slower, the more data exists and has to be validated.

Why is PouchDB so slow?

For the PouchDB and RxDB (with PouchDB storage) I used the old Indexeddb adapter. It is much less optimized than the new adapter, but the new one made problems with returning the correct query results. Theses problems have been fixed on the PouchDB master branch, but I have to wait for the next PouchDB release. I will update the repo when this change can be done.

Why does AWS Datastore need so much less storage space?

AWS Datastore does not save any metadata together with the documents. Instead only the plain documents are stored in IndexedDB. They can do this because they only allow simple queries and do not keep a local version history.

Feature Map

Feature \ Project	aws	firebase	pouchdb	rxdb-pouchdb	rxdb-lokijs	rxdb-dexie	watermelondb
Offline First	No, login required	Partially, must be online on first page load	Yes	Yes	Yes	Yes	Yes
Realtime Replication	Yes	Yes	Yes	Yes	Yes	Yes	Partially, must be implemented by hand
Multi Tab Support	Yes	Yes	No	Yes	Yes	Yes	Partially, relies on online sync
Observable Queries	No	Yes	No	Yes	Yes	Yes	Yes
Complex Queries	No	Yes	Yes	Yes	Yes	Yes	Yes
Client Side Encryption	No	No	Yes	Yes	Yes	Yes	No
Schema Support	Yes	No	No	Yes	Yes	Yes	Yes
Custom Backend	No	No	No	Yes	Yes	Yes	Yes
Custom Conflict Handling	Yes	No	Yes	Yes	No	No	No

Starting the projects

All sub-projects use the same port and so can not be started in parallel.

Installation

• You must have installed Node.js
• Clone this project
• In the root folder, run npm install to install the dependencies.
• In the root folder, run npm run build to build all projects.

Firebase Firestore

• Run npm run start:firebase to start the mock server and the production build frontend.

• Or run npm run dev:firebase to start the mock server and the development frontend server.

• Open http://localhost:3000/ to browse the frontend.

AWS Amplify & Datastore

The official AWS mock does not allow a live replication at this point. So you first have to setup an amplify project in the ./projects/aws folder by using this tutorial

• Run npm run start:aws to start the mock server and the production build frontend.

• Or run npm run dev:aws to start the mock server and the development frontend server.

• Open http://localhost:3000/ to browse the frontend.

PouchDB

• Run npm run start:pouchdb to start the mock server and the production build frontend.

• Or run npm run dev:pouchdb to start the mock server and the development frontend server.

• Open http://localhost:3000/ to browse the frontend.

RxDB PouchDB

• Run npm run start:rxdb-pouchdb to start the mock server and the production build frontend.

• Or run npm run dev:rxdb-pouchdb to start the mock server and the development frontend server.

• Open http://localhost:3000/ to browse the frontend.

RxDB LokiJS

• Run npm run start:rxdb-lokijs to start the mock server and the production build frontend.

• Or run npm run dev:rxdb-lokijs to start the mock server and the development frontend server.

• Open http://localhost:3000/ to browse the frontend.

RxDB Dexie.js

• Run npm run start:rxdb-dexie to start the mock server and the production build frontend.

• Or run npm run dev:rxdb-dexie to start the mock server and the development frontend server.

• Open http://localhost:3000/ to browse the frontend.

WatermelonDB

• Run npm run start:watermelondb to start the mock server and the production build frontend.

• Or run npm run dev:watermelondb to start the mock server and the development frontend server.

• Open http://localhost:3000/ to browse the frontend.

TODOs

Pull requests are welcomed. Please help implementing more examples:

• Meteor (with the IndexedDB offline first plugin).
• WatermelonDB backend replication.
• AWS Ampflify local backend mock with realtime replication.
• GunDB.