Why Google ADK over CrewAI
Google ADK integrates natively with Vertex AI Gemini 2.5 and fits this architecture immediately. We use Gemini 2.5 Pro for the Manager and Outreach agents where reasoning quality matters most, and Gemini 2.5 Flash for Scout, Researcher, Scorer and Followup where speed is the priority.
Why SSE over WebSockets
Server-Sent Events are simpler, more reliable, and perfectly suited for one-directional agent trace streaming. No connection management overhead.
Why Firestore over PostgreSQL
Firestore's schemaless nature matched our evolving lead data structure. Zero configuration, auto-scaling, native GCP integration.
Why two Gemini models instead of one
Gemini 2.5 Pro produces noticeably better cold email personalization and orchestration reasoning. Gemini 2.5 Flash is 10x cheaper and fast enough for structured data extraction. Using both optimizes quality where it matters and speed everywhere else.