Summary
Problem of Concurrency comes in picture when two or more threads /process or user try to work with same data.
There are several patterns that deals with Concurrency pattern and each optimized to a particular business problems.
Concurrency Vs Synchronization
Synchronization deal at very low level and it`s focus is to prevent the incorrect R/W due to thread racing issues.
Concurrency implement policy that decide what to do when a such conflict happens.
Concurrency Patterns Index