DSAR response SLAs in practice: what turnaround times are realistic at 500+ requests/month?

We're scaling our DSAR (Data Subject Access Request) pipeline and hitting a wall around the 400-500 requests/month mark. The GDPR Art. 12(3) one-month deadline is clear on paper, but operationalizing it across multiple data sources is brutal. How have teams handled this at scale? Are you using automated data discovery tools, or is it still heavily manual? What SLAs are you actually hitting in practice vs. what the regulation says? Jurisdiction: EU, DE