Concurrent connections (or concurrency) is the number of simultaneous requests a proxy plan supports at once. Higher concurrency means faster scraping — you can parallelize across many IPs simultaneously rather than waiting for each request to complete before firing the next.
Concurrency limits are a key pricing differentiator among proxy providers. Entry plans might allow 10–50 concurrent connections; enterprise plans can run thousands. For large-scale scraping pipelines, practical throughput is usually concurrency × request speed — raising concurrency is often the fastest way to scale a working scraper.