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Most programming approaches (procedural, object-oriented, functional, applicative, logical) assume nothing about the threadedness of the environment. Most technologies in CS in fact require additional support for multi-threading.
DCI provides no explicit facilities for either multithreading or parallelism. Neither does procedural programming or object-oriented programming. Parallel and multithreaded programs nonetheless exist in both procedural and object-oriented programming languages. There is no fundamental reason why they can't exist in a DCI implementation.
Regarding function callbacks, lambda expressions or similar asynchronous concepts, there is no hindrance using them in DCI.