MongoDB A quick overview Brad - @darb – Dev/Ops manager, Motribe 

Structure of my talk Context / How we are using MongoDB Terminology in MongoDB world Deployment / Growing The things that suck 

What we do - 3 web apps, 1 MongoDB cluster ‧ Motribe - mobile social network ● ±50k monthly active users ‧ JudgeMe – mxit social app ● 1m signups in 45 days / 200k+ photo uploads ● 0.5m - 3m pageviews/day ‧ MxPix – mxit photo sharing app ● 200k+ signups in a week / 70k+ photo uploads ● 0.5m – 1m page views/day 

MongoDB (from "humongous") ‧ JSON Document storage ‧ Documents are members of Collections ‧ Collections belong to Databases ‧ Indexes on any key in a document ‧ Javascript interface for queries ‧ Trivial Sharding of data 

Some benefits ‧ Implicit creation of databases, collections ‧ Index and query anything inside document (composite keys, 2d/geo indexing) ‧ Great documentation ‧ Great examples (e.g. randomization) ‧ Emphasis on Just Works™ ‧ Drivers in many languages ‧ Active community 

Grow up or out ‧ Horizontal – read/write throughput ● Shard databases - split collections over shards ● Shard collections - split documents over shards ‧ Vertical – read throughput ● Replica sets – Auto master / slaves, voting, promotion, demotion – Time delayed slaves – Magic... bring up mongo server, inform config server, siphons data 

Moving parts at scale ‧ Routers – “mongos” ● Abstract the magic, route requests to the right place ● Collate responses from shards, etc. ● Apps connect to “mongos” ‧ Config servers ● Min 3x for redundancy ● Knows about dbs, shards, slaves 

A picture 

Monitoring ‧ Mongo Monitoring Service (MMS) is lovely ‧ JS console means you can do powerful things on the terminal ‧ JS interface exposes lots of data ● Size of indexes ● Comprehensive info about where db/collections stored ● Location, status and health of nodes 

The things that suck ‧ Index anything means indexes can get large (e.g. we have 4gb of indexes on a big collection) ‧ You need to aim to have all indexes+data in ram ‧ MapReduce is available but meh ● Improving with each release, possible to hack onto hadoop 

More of the things that suck ‧ Implicit creation means mis-spelled dbs, collections == WTF ‧ B-tree indexes mean queries/insertion by _id are O(log n) not O(1) ala pure key/value stores