  - Current infrastructures for developing big-data applications are able to
process --via big-data analytics-huge amounts of data, using clusters of
machines that collaborate to perform parallel computations. However, current
infrastructures were not designed to work with the requirements of
time-critical applications; they are more focused on general-purpose
applications rather than time-critical ones. Addressing this issue from the
perspective of the real-time systems community, this paper considers
time-critical big-data. It deals with the definition of a time-critical
big-data system from the point of view of requirements, analyzing the specific
characteristics of some popular big-data applications. This analysis is
complemented by the challenges stemmed from the infrastructures that support
the applications, proposing an architecture and offering initial performance
patterns that connect application costs with infrastructure performance.
