The subject of this research is the development of the architecture of expert system for distributed content aggregation system, the main purpose of which is the categorization of aggregated data. The author examines the advantages and disadvantages of expert systems, toolset for development of expert systems, classification of expert systems, as well as application of expert systems for categorization of data. Special attention is given to the description of architecture of the proposed expert system, which consists of spam filter, component for determination of the main category for each type of the processed content, and components for determination of subcategories, one of which is based on the domain rules, and the other uses the methods of machine learning methods and complements the first one. The conclusion is made that expert system can be effectively applied for solution of the problems of categorization of data in the content aggregation systems. The author establishes that hybrid solutions, which combine an approach based on the use of knowledge base and rules with implementation of neural networks allow reducing the cost of the expert system. The novelty of this research lies in the proposed architecture of the system, which is easily extensible and adaptable to workloads by scaling existing modules or adding new ones. The proposed module for spam detection leans on adapting the behavioral algorithm for detecting spam in emails; the proposed module for determination of the key categories of content uses two types of algorithms: fuzzy fingerprints and Twitter topic fuzzy fingerprints that was initially applied for categorization of messages in the social network Twitter. The module that determine subcategory based on the keywords functions in interaction with the thesaurus database. The latter classifier uses the reference vector algorithm for the final determination of subcategories.