Key-Value
A key-value pair is a tuple of two strings: a unique identifier (key) associated to a value.
Requests are quick and basic, limited to crud operations
Usages: session information, users profiles/preferences, shopping cart, etc.
Principle of hashmap, stored persistently on disk
MapReduce
MapReduce is a framework that simplifies the distribution of large collections of data across multiple servers.
Steps
- Split: divide input data into subsets key-value pairs.
- Map: do a process on each subset
- Shuffle: group and sort all values by key
- Reduce: iIterate over groups and aggregate values of each group