Notes from "Blending MongoDB and RDBMS for eCommerce"

github.com/spf13
spf13.com
@spf13
OpenSky eCommerce platform

products in mongo using custom fields for different product types (i.e. actors in movie, tracklist for album etc)

- ordered items need to be fixed at time of purchase, table inheritance bad for this

## 3 things for e-commerce

- optimistic concurrency (update if current, then try again if document is not current)
- assumes environment with low data contention
- works well for Amazon with long tail product catalogue
- works bad for ebay, groupe, anything with flash-sales (high data contention)

# Commerce is ACID in real-life

purchasing something from a store deals with this without concurrency as each product can only be held by one customer

MongoDB e-Commerce

- each item (not sku) has it's own document
- contains
-- reference to sku
-- state
-- other meta-data (timestamp, order ref etc)

cart in card action difficult, but in Mongo changing state on item makes it unavailable to other customers (e.g. if state is 'in-cart')

## Blending

Doctrine (OS - ORM/ODM) modelled on Hibernate

in SQL
-- product inventory, sellable inventory, orders

- inventory is transient in Mongo collections
- inventory kept in sync with listeners

for financial transactions we want security and comfort of RDBMS

## Playing Nice

products are stored in a document
orders are entities stored in relational DB
store reference not relationships across two databases

jwage.com/2010/08/25/blending-the-doctrine-orm-and-mongdb-odm/