MongoDB has taken a clear lead in adoption among the new generation of databases, including the enormous variety of NoSQL offerings. A key reason for this lead has been a unique combination of agility and scalability. Agility provides business units with a quick start and flexibility to maintain development velocity, despite changing data and requirements. Scalability maintains that flexibility while providing fast, interactive performance as data volume and usage increase. We'll address the key organizational, operational, and engineering considerations to ensure that agility and scalability stay aligned at increasing scale, from small development instances to web-scale applications. We will also survey some key examples of highly-scaled customer applications of MongoDB.

1. MongoDB
Scalability and Agility
Chris.Biow@MongoDB.com

2. Data Challenge
“I want my data...”
• Now
• Secure
• All varieties
• Fast and interactive
• Scalable to “Big”
• Agile to develop and deploy operationally
• Cloud and edge
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iStock licensed (pixelfit)

3. Scalability with MongoDB
Metric Meaning Examples
Operations per
Second
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Concurrent reads and writes per
second
> 1 Million per second
Nodes per
Cluster
Horizontal scale-out, distributed to
multiple data centers worldwide, with
high availability, using inexpensive
cloud resources
> 1000 nodes
Records /
Documents
Data objects in any number of
schemas or structures
> 10 billion
Data Volume Total amount of data: documents X
size
> 1 Petabyte
= 10^15
= 1,000,000,000,000,000
≈ 2^50

4. Key Differentiation

5. Operational Database Landscape
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6. Document Data Model
Relational MongoDB
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{
first_name: ‘Paul’,
surname: ‘Miller’,
city: ‘London’,
location:
[45.123,47.232],
cars: [
{ model: ‘Bentley’,
year: 1973,
value: 100000, … },
{ model: ‘Rolls Royce’,
year: 1965,
value: 330000, … }
}
}

7. Documents are Rich Data Structures
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{
first_name: ‘Paul’,
surname: ‘Miller’,
cell: ‘+447557505611’
city: ‘London’,
location: [45.123,47.232],
Profession: [banking, finance, trader],
cars: [
{ model: ‘Bentley’,
year: 1973,
value: 100000, … },
{ model: ‘Rolls Royce’,
year: 1965,
value: 330000, … }
}
}
Fields can contain an array of
sub-documents
Fields
Typed field values
Fields can
contain arrays

8. Document Model Benefits
• Agility and flexibility
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– Data model supports business change
– Rapidly iterate to meet new requirements
• Intuitive, natural data representation
– Eliminates ORM layer
– Developers are more productive
• Reduces the need for joins, disk seeks
– Programming is more simple
– Performance delivered at scale

9. Big Data Tech Interest Comparison
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j.mp/Ssvpev

10. Enterprise Adoption Comparison
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bit.ly/1vAI7rF

11. Architecture for
Availability & Scalability

12. Replica Sets
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• Replica Set – two or more copies
• Availability solution
– High Availability
– Disaster Recovery
– Maintenance
• Deployment Flexibility
– Data locality to users
– Workload isolation: operational &
analytics
• Self-healing shard
Application
Driver
Primary
Secondary
Secondary
Repl ication

13. Global Data Distribution
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Real-time
Real-time Real-time
Real-time
Real-time
Real-time
Real-time
Primary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary

14. Automatic Sharding
• Sharding types
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• Range
• Hash
• Tag-aware
• Elastic increase or decrease in capacity
• Automatic balancing

15. Query Routing
• Multiple query optimization models
• Each sharding option appropriate for different apps
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16. Performance

17. Drag Strip:
straight ahead, quarter-mile, stop
20

18. Road Race:
stay fast, stay agile, continuous
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Nürburgring, Germany

19. MongoDB at Scale

20. CarFax
• Large data set
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21. 25
Baseline MongoDB Comparison Initial Production
• Vehicle History
Database
• 11 billion records
(growing at 1 billion per
year)
• 30-year-old VMS-based
RDBMS
• Cumbersome
• Costly
• Performance: 4x faster
than baseline, 10x key-value
• Scale out using
inexpensive commodity
servers
• Built-in redundancy
• Flexible dynamic schema
data model
• Strong consistency
• Analytics/aggregation
• MongoDB is primary data
store
• 50 servers
• 10 shards
• 5 node replica sets per
shard
In-depth NoSQL evaluation

22. CARFAX Sharding and Replication
• 13 billion+ documents
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– 1.5 billion documents added every year
• 1 vehicle history report is > 200 documents
• 12 Shards
• 9-node replica sets
• Replicas distributed across 3 data centers

23. CARFAX Replication
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24. 28

25. Foursquare
• 50M users.
• 6B check-ins to date (6M per day growth).
• 55M points of interest / venues.
• 1.7M merchants using the platform for marketing
• Operations Per Second: 300,000
• Documents: 5.5B (~16.5B with replication).*
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26. Foursquare clusters
• 11 MongoDB clusters
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– 8 are sharded
• Largest cluster for check-ins
• 15 shards (check ins)
• Shard key user_id

27. Facebook / parse.com mobile apps
• Persistent database for 270,000 mobile applications
• 200 M end-user mobile devices
• 250% annual growth in client apps
• 500% growth in requests
• 1.5 M collections
• Key differentiators:
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– Document data model
– High perf. & avail.
– Geospatial query and index
• Charity Majors operations: j.mp/X3jVRC
– Understand your database and your data, and build for them.

29. Scalability Exercises in the Cloud
with Amazon Web Services

30. Petascale Database
• 27x hs1.8xlarge instances
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– 16x VCPU
– 24x 2TB SATA drives, RAID0
– 8x mongod microshards
• Modified Yahoo Cloud Serving
Benchmark (YCSB)
– Long Integer IDs (>2B)
– Zipfian-distributed integer fields
– Aggregation queries
• Load direct to 216 shards, 10 days, $4K
"objects" : 7,170,648,489,
"avgObjSize" : 147,438.99952658816,
"dataSize" : NumberLong("1,057,240,224,818,640")
(commas added)

31. CGroup Memory Segregation
for DB in `seq 0 3`; do
sudo cgcreate
-a mongodb:mongodb
-t mongodb:mongodb
-g memory:mongodb$D
sudo echo 48G >
/sys/fs/cgroup/memory/mongodb$D/memory.limit_in_bytes
cgexec
-g memory:mongodb$DB
numactl –interleave=all
mongod –-config ~/mongod$DB.conf
done

32. Megawrite Ingest
• Ingest 250-byte stock quotes at 2M/s
• Concurrently run 5 QPS, subsecond/indexed response on
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timeStamp, accountId, instrumentId, systemKey
• 5x r3.4xlarge
– 16x VCPU, 1x 320GB SSD, 122GB RAM, 16x mongod
– 2.1M insert/second direct to shards
• 16x c3.8xlarge
– 32x VCPU, 2x 320GB SSD, 60GB RAM, 16x mongod, 4x mongos
– 2.1M insert/second via mongos

33. Java API comparison
• 2 threads on c3.8xl
• 264 bsonsize object, _id index only
• coll.insert()
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15,600 ins / sec
• coll.insert(List<DBObject>)
listsize = 64: 118,000 ins / sec
• Bulk ops API
size = 64: 120,000 ins / sec

34. BulkWriteOperation bo = null;
for(a = 0; a < this.items && stayAlive; a++) {
if(bo == null) {
bo = collection.initializeUnorderedBulkOperation();
}
fillMap(this.m);
BasicDBObject dbObject = new BasicDBObject(this.m);
bo.insert(dbObject);
if(0 == a % listsize) {
BulkWriteResult rc = bo.execute();
bo = null;
}
}
7x Load with BulkOp

35. How do I Pick A Shard Key?

36. Shard Key characteristics
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• A good shard key has:
– sufficient cardinality
– distributed writes
– targeted reads ("query isolation")
• Shard key should be in every query if possible
– scatter gather otherwise
• Choosing a good shard key is important!
– affects performance and scalability
– changing it later is expensive

37. Hashed shard key
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• Pros:
– Evenly distributed writes
• Cons:
– Random data (and index) updates can be IO intensive
– Range-based queries turn into scatter gather
Shard 1
mongos
Shard 2 Shard 3 Shard N

38. Low cardinality shard key
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• Induces "jumbo chunks"
• Examples: boolean field
Shard 1
mongos
Shard 2 Shard 3 Shard N
[ a,
b )

39. Ascending shard key
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• Monotonically increasing shard key values
cause "hot spots" on inserts
• Examples: timestamps, _id
Shard 1
mongos
[ ISODate(…),
$maxKey )
Shard 2 Shard 3 Shard N

40. Ensuring Success with
High Scalability

41. Success Factors
• Storage: random seeks (IOPS)
• RAM: working set based on query patterns
• Query: indexing
• Delete: most expensive operation
• Real-time vs. bulk operations
• Continuity: HA, DR, backup, restore
• Agile process: iterate by powers of 4
• Sharding: shard key and strategy
• Resources: don’t go it alone!
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