Two-Plane Model

Pramiti's architecture separates concerns into two independent planes that share a common platform layer but can be deployed and scaled independently.

Read Plane (Epistom)Copy Anchor Link

The read plane answers: "What does this data mean?"

Components:

• Knowledge Model (OWL 2 QL in Oxigraph)
• NLQ Engine (query routing, SQL generation, validation)
• MCP Server (8 tools for agent connectivity)
• Verified Queries (curated SQL patterns)
• Drift Detection (schema change monitoring)
• Feedback Engine (self-improving accuracy)

Dependencies: PostgreSQL + Oxigraph + LLM

The read plane operates exclusively on read-only database connections. The EPISTOM_SQL_READONLY=true setting ensures LLM-generated SQL cannot modify source databases.

Write Plane (Praxom)Copy Anchor Link

The write plane answers: "Is this action valid?"

Components:

• Policy Decision Point (constraint evaluation)
• Constraint Engine (JSON predicates + SHACL)
• Impact Engine (blast radius computation)
• Attestation Store (Ed25519 signing, append-only)
• Connection Manager (downstream MCP servers)
• SIEM Integration (OCSF delivery)

Dependencies: PostgreSQL is the system of record. Redis is used for budget counters and taint when those slots are configured. No Oxigraph, no LLM.

The write plane is deliberately simple and auditable. It has no LLM dependency, no Oxigraph dependency, and no non-deterministic components. Every evaluation produces the same result given the same inputs.

Independent DeploymentCopy Anchor Link

The two planes can be deployed independently:

# Epistom only (read plane)
docker compose --profile epistom up -d

# Praxom only (write plane)
docker compose --profile praxom up -d

# Both planes (full platform)
make up

Each has its own API entry point (epistom_main.py, praxom_main.py, main.py) with the appropriate routers included.

Shared Platform LayerCopy Anchor Link

Both planes share:

• Authentication — JWT, SAML SSO, Azure AD, API keys
• Tenancy — Workspace-based data isolation
• Audit — Append-only audit log with HMAC tamper detection
• Rate Limiting — Per-key rate limiting with Redis support
• Billing — Stripe integration for cloud deployments

Why Two Planes?Copy Anchor Link

Separating reads and writes provides:

1. Independent scaling — The read plane needs LLM capacity; the write plane needs policy evaluation throughput
2. Different trust models — The read plane involves LLM (non-deterministic); the write plane is fully deterministic
3. Different buyers — VP Data buys Epistom; CISO buys Praxom
4. Blast radius isolation — A compromise in the read plane doesn't affect write-plane enforcement
5. Regulatory clarity — Auditors can verify the write plane independently of the read plane