Yes, Open CSP is scalable
Open CSP is scalable because it builds in an efficient way on MediaWiki and Elasticsearch.
MediaWiki is scalable
MediaWiki has been designed with scalability in mind for high-usage, high-profile sites.
Elasticsearch is scalable
Elasticsearch is built to be always available and to scale with your needs. It does this by being distributed by nature. You can add servers (nodes) to a cluster to increase capacity and Elasticsearch automatically distributes your data and query load across all of the available nodes.