Gregor Hohpe is a software architect with Google, Inc. Gregor is a widely recognized thought leader on asynchronous messaging architectures and service-oriented architectures. He coauthored the seminal book Enterprise Integration Patterns (Addison-Wesley Professional) and speaks regularly at technical conferences around the world.
ENGINEERS LIKE PRECISION, especially software engineers who live in the realm of ones and zeros. They are used to working with binary decisions, one or zero, true or false, yes or no. Everything is clear and consistent, guaranteed by foreign key constraints, atomic transactions, and checksums.
Unfortunately, the real world is not quite that binary. Customers place orders, only to cancel them a moment later. Checks bounce, letters are lost, payments delayed, and promises broken. Data entry errors are bound to happen every so often. Users prefer "shallow" user interfaces, which give them access to many functions at once without being boxed into a lengthy, one-dimensional "process," which is easier to program and seems more "logical" to many developers. Instead of the call stack controlling the program flow, the user is in charge.
Worse yet, widely distributed systems introduce a whole new set of inconsistencies into the game. Services may not be reachable, change without prior notice, or do not provide transactional ...