
NeuralSearchX: Serving a Multi-billion-parameter
Reranker for Multilingual Metasearch at a Low Cost
Thales Sales Almeida*, Thiago Laitz*, João Seródio*, Luiz Henrique Bonifacio,
Roberto Lotufo and Rodrigo Nogueira
NeuralMind, Brazil
Abstract
The widespread availability of search API’s (both free and commercial) brings the promise of increased
coverage and quality of search results for metasearch engines, while decreasing the maintenance costs
of the crawling and indexing infrastructures. However, merging strategies frequently comprise complex
pipelines that require careful tuning, which is often overlooked in the literature. In this work, we describe
NeuralSearchX, a metasearch engine based on a multi-purpose large reranking model to merge results
and highlight sentences. Due to the homogeneity of our architecture, we could focus our optimization
eorts on a single component. We compare our system with Microsoft’s Biomedical Search and show
that our design choices led to a much cost-eective system with competitive QPS while having close to
state-of-the-art results on a wide range of public benchmarks. Human evaluation on two domain-specic
tasks shows that our retrieval system outperformed Google API by a large margin in terms of nDCG@10
scores. By describing our architecture and implementation in detail, we hope that the community will
build on our design choices. The system is available at https://neuralsearchx.neuralmind.ai.
Keywords
Metasearch, Merging strategies, Transformers
1. Introduction
Metasearch engines provide a unied interface for searching and aggregating results from
dierent sources. They take advantage of existing search engines to increase the diversity of
results while decreasing maintenance costs for crawling and indexing infrastructures.
This approach, however, comes with a unique set of challenges: many times metasearch
engines choose to consult only sources that might be relevant to a given query, since searching
all available collections may be unfeasible due to resource constraints, such as limited bandwidth.
For example, given a medical-related query, a metasearch engine could choose to consult only
search engines that are capable of returning medical-related content. Therefore, a metasearch
engine must represent the capabilities and type of data that each source search engine provides,
i.e., the representation problem. When receiving a query, the metasearch engine must be able
to select the appropriate sources, i.e., the selection problem. Furthermore, a metasearch engine
is also responsible for generating a unied list of results from the multiples lists that it retrieves
DESIRES 2022 – 3rd International Conference on Design of Experimental Search & Information REtrieval Systems, 30-31
August 2022, San Jose, CA, USA
*Equal contribution.
"thalesrogerio@gmail.com (T. S. Almeida*)
©2022 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
CEUR
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ISSN 1613-0073
CEUR Workshop Proceedings (CEUR-WS.org)
arXiv:2210.14837v1 [cs.IR] 26 Oct 2022