Anyone successfully connected to SAT API Mexico for automated RFC and CFDI validation?

We are building a digital lending product in Mexico and need to integrate with SAT API Mexico to validate borrower tax information before disbursement. Our compliance team requires that we verify RFC status, pull constancia fiscal data, and cross-check against the 69-B blacklist on every single loan application.

The challenge is that SAT's official web services are notoriously painful to work with. Their SOAP-based endpoints require authentication via FIEL (Firma Electrónica Avanzada) certificates, which adds complexity to our Node.js backend. Documentation on the SAT portal is sparse — mostly PDFs in Spanish with outdated endpoint references that don't match what actually works.

Our specific integration needs for SAT API Mexico:

• Real-time RFC validation — confirm the RFC is active and matches the taxpayer name
• Constancia de situación fiscal — retrieve the full fiscal profile including tax regime, registered address, and economic activities
• Lista negra 69-B and 69-B bis lookup — ensure the applicant isn't flagged for fictitious invoicing
• CFDI metadata retrieval — query issued and received invoices for the past 12 months to estimate income
• Opinión de cumplimiento — check if the taxpayer has a positive compliance opinion

We already attempted direct integration with SAT's SOAP services. Problems included constant timeouts during business hours (roughly 10am to 3pm Mexico City time), rate limiting after just 50 requests per hour, and XML responses that vary in structure between different SAT service versions. Our team spent three weeks on this before deciding to look for alternatives.

What we are considering now is using a third-party SAT API Mexico provider that abstracts the complexity. Ideally something with REST endpoints, JSON responses, reasonable latency (under 500ms), and proper error handling when SAT itself is down. We'd also want webhook notifications for asynchronous operations like bulk CFDI downloads.

Has anyone here integrated with a SAT API Mexico provider through an API marketplace? What was your experience with data freshness — specifically, how often do these providers sync cached data with SAT's actual databases? For lending use cases stale data could be a serious compliance risk.

Budget-wise we're looking at pay-per-query pricing rather than fixed monthly. Processing around 200-500 RFC validations daily initially, scaling to 2000+ within six months.