The document discusses the use of MongoDB for mobile app backends, highlighting its advantages such as scalability, high performance, and flexible data storage through a JSON-like structure. It provides insights into how MongoDB addresses common database challenges, including object-relational impedance mismatch and the need for horizontal scalability. Additionally, it mentions use cases, including geospatial indexing and a cloud-hosted MongoDB solution via Mongolab, while also noting limitations in performing complex transactions.

1. MongoDB for mobile app
backends
sf android meetup
08.31.2010

2. I’ve written my mobile app…
where should I store my data ?
?

3. Mobile apps do not exist
in a vacuum
• user profile data
• logging
• location-based data collection
• game data (stats, high scores)
• polls and surveys
• user feedback

4. Do I want to host this
myself ?
Java + Spring + Hibernate ?
Ruby on Rails ?
Hmmm… I will probably
need to build a REST API…

5. GET, POST, PUT, DELETE
•EC2
•Rackspace
•App Engine*
•MySQL
•SQLServer
•Postgres
•RoR
•J2EE
General approach
REST API

6. How can this be even simpler and
more awesome?

7. • “Scalable, open-source, high-
performance, document-oriented
database” - 10gen
• “The database your database could
smell like” - old spice guy

8. MongoDB is designed to address
two modern DB problems
1. object / relational “impedance mismatch”
2. horizontal scalability

9. Native drivers in almost every
language
• Java
• Javascript
• Python
• Ruby
• C#
• PHP
• and more…

10. A paradigm shift…
• Traditional RDMS
– database
– table
– row
• MongoDB
– database
– collection
– document / object

11. Documents (a.k.a. Objects)
{
_id: 1234,
author: { name: “Bob Jones”, email: “b@b.com” },
post: “In these troubled times I like to …“,
date: { $date: “2010-07-12 13:23UTC” },
location: [ -121.2322, 42.1223222 ],
rating: 2.2,
comments: [
{ user: “jgs32@hotmail.com”,
upVotes: 22,
downVotes: 14,
text: “Great point! I agree” },
{ user: “holly.davidson@gmail.com”,
upVotes: 421,
downVotes: 22,
text: “You are a moron” }
]
}

12. {
_id: 1234,
author: { name: “Bob Jones”, email: “b@b.com” },
post: “In these troubled times I like to …“,
date: { $date: “2010-07-12 13:23UTC” },
location: [ -121.2322, 42.1223222 ],
rating: 2.2,
comments: [
{ user: “jgs32@hotmail.com”,
upVotes: 22,
downVotes: 14,
text: “Great point! I agree” },
{ user: “holly.davidson@gmail.com”,
upVotes: 421,
downVotes: 22,
text: “You are a moron” }
],
tags: [ “politics”, “Virginia” ]
}
Flexible “schemas”

13. db.posts.find({ author.name: “mike” })
Dynamic queries
db.posts.find({ rating: { $gt: 2 }})
db.posts.find({ tags: “software” })
db.posts.find().sort({date: -1}).limit(10)

14. Comment c = {author: “will”,
date: new Date(),
text: “great post!”}
db.posts.update({_id: post._id},
{$push: {comments: c}})
Atomic update operators

15. Aggregation and Map/Reduce

16. Focus on scalability and
performance

17. depth of functionality
scalabilityandperformance
•memcached
•key / value
•RDBMS
•

18. High performance, fault tolerant
clusters made easy
• master / slave replication
• replica sets
• auto-sharding

19. MongoDB is great for mobile
• everything is JSON!
– storage model is JSON
– queries are in JSON
– update operators are in JSON
• geospatial indexing built-in
• GridFS

20. Geospatial indexing
• index on geo coordinate pairs
• search by
– bounding box
– bounding circle (point, radius)

21. Geospatial indexing
db.places.ensureIndex( { loc: “2d” } )
db.places.find({ loc: { $near : [50, 50] } }).limit(10)
db.places.find({loc: {$within : {$box : [[40,40],[60,60]]}}})
db.places.find({loc: {$within : {$center : [[40,40],10]}}})

22. Geospatial indexing at
Foursquare
• ~1.3M registered users
• ~615k check-ins a day
• “Who’s here” service tracks last 3 hours for
every user; uses mongo exclusively
• all checkins, tips and venues written to
mongo; reads a mix of mongo / legacy
postgres

23. GridFS
• distributed filesystem inside MongoDB
• stores large files by splitting them into
smaller documents
• leverages existing sharding and
replication configuration
• stores metadata along with files
• works well behind a CDN

24. Street cred
• Shutterfly
• Foursquare
• bit.ly
• Sourceforge
• Etsy
• The New York Times
• Business Insider
• Github
• Gilt Groupe
• Sugar CRM
• Electronic Arts
• Evite
• CollegeHumor
• Disqus
• Justin.tv
• Chartbeat
• Hot potato
• Eventbrite

25. Not so good for
• Complex / multi-operation
transactions
• When you (really) need joins

26. How can this be even simpler and
more awesome?

27. • MongoLab provides cloud-hosted
MongoDB
• It’s EC2 hosting + MongoDB + REST
API + awesome admin tools
• http://mongolab.com

28. GET, POST, PUT, DELETE
EC2
MongoDB
Two ways to use MongoLab
REST API
method 1: REST API
method 2: MongoDB driver
Your application

29. /databases/<d>/collections
GET
/databases/<d>/collections/<c>
GET
POST
/databases/<d>/collections/<c>/<_id>
GET
PUT
DELETE
/databases/<d>/collections/<c>?[q=<query>]
[&f=<fields>]
[&s=<order>]
[&sk=<skip>]
[&l=<limit>]
GET
MongoLab API

30. Example app:
GeoPost
• add a GeoPost (email, date, message, location)
• list nearby GeoPosts

31. Example app:
GeoPost
• POST
URL: https://mongolab.com/api/1/databases/demo/collections/geoposts
data: { “email” : “will@mongolab.com”,
“date” : { “$date” : “2010-02-03 10:21:21 UTC” },
“location” : { “lat” : 41, “long” : -82 },
“message” : “Hello Cleveland!” }
• GET
URL: https://…/geoposts?q={"location":{"$near":{"lat":38,"long":-122}}}

33. Android SDK makes client-side
easy
• JSON: org.json.*
• REST: org.apache.http.*
HttpClient client = new DefaultHttpClient()
HttpGet request = new HttpGet(url);
HttpResponse response = client.execute(request);
HttpEntity entity = response.getEntity();
InputStream in = entity.getContent();
String json = convertStreamToString(in);
JSONObject o = new JSONObject(json);

34. For more info…
• MongoDB / 10Gen
– http://mongodb.org
– http://10gen.com
• MongoLab
– http://mongolab.com
– will@mongolab.com