Concurrency limits: the cheap plan can stop being the usable plan
A concurrency limit is the number of requests or sessions a plan permits at the same time. It is a feasibility limit before it is a price feature. If a plan cannot run the buyer’s required parallel workload, its checkout price is not a valid cost for that job. The buyer must reduce throughput, wait longer, or purchase more capacity. Dataset snapshot, all evidence retrieved 2026-07-25
The cap that changes after a traffic threshold
oxylabs-isp-semi-dedicated-10-ips costs $16 per month for 10 IPs. Oxylabs publishes 100 concurrent sessions per purchased IP while usage is at or below 50 GB per IP per month. After an IP exceeds 50 GB, its allowance falls to 10 concurrent sessions. One top-line concurrency number cannot describe both states. Oxylabs ISP pricing, retrieved 2026-07-25T15:31:32Z
Suppose a workload needs 1,000 simultaneous sessions and every purchased IP has crossed that 50 GB threshold. The 10-IP row then supports 100 sessions at the published post-threshold rate, not 1,000. The matching oxylabs-isp-semi-dedicated-100-ips row costs $130 per month and applies the same 10-sessions-per-IP rule after the threshold, which is enough for 1,000 sessions across 100 IPs. The concurrency schedule changes the qualifying checkout from $16 to $130 for that stated workload. Oxylabs ISP pricing, retrieved 2026-07-25T15:31:32Z
This example also shows why the unit matters. A cap may be per IP, per port, per account, or per plan. Multiplying a per-IP cap by the purchased IP count is valid only while every condition attached to that cap remains true. A usage threshold, fair-use rule, or plan tier can change the result during the billing period. Oxylabs ISP pricing, retrieved 2026-07-25T15:31:32Z
Not published is not unlimited
The current dataset records concurrent_sessions_max: null on 472 of 710 plan rows. Those rows cannot satisfy a concurrency requirement in a comparison, because the provider did not publish a usable value in the evidence collected. Another 165 rows explicitly use the unrestricted value unlimited; that is a different state and must remain different. Dataset snapshot, all evidence retrieved 2026-07-25
Before comparing prices, write down the required simultaneous sessions and check whether the vendor’s number is per IP or per account, whether it changes with usage, whether “threads” and “sessions” are stated separately, and whether the limit applies to every rotation mode. A cheap row that fails any of those requirements should be excluded rather than assigned an optimistic capacity. Dataset methodology and plan evidence, retrieved 2026-07-25