The QPS limit can be raised by submitting a request to Google Support on the Edit Quotas page. Choose the API (for example Geocoding API) and either per project or per user, depending on your needs. Quotas are per project and shared across API keys within a project. Since this is the case, another strategy to increase quotas is to create additional projects and spread traffic across multiple projects.
Note: Client IDs don't have the option to set quotas.
50 QPS = 5000 queries/100s. It is possible to execute all 5000 queries in 10s (rate of 500/s). It would then be required to wait a mandatory 100s for the quota to refill.