Mortar — Bring Your Own Cloud (BYOC)

Status: design doc; first customer pilot planned. Aliyun + AWS only at first; GCP / Azure added when a paying customer asks for them.

BYOC lets enterprises run Mortar’s data plane in their own cloud account, while Mortar’s control plane orchestrates from our account. Mortar never touches customer data; we only issue credentials, push config, and read aggregate usage metrics.

This unblocks deployments at Fortune 500 / regulated industries (banks, hospitals, government) where data leaving the customer’s VPC is a non-starter.

TL;DR

• Data plane (the customer’s data) lives entirely in the customer’s AWS / Aliyun account: RDS Postgres, OSS / S3, Redis / ElastiCache, FC / Lambda, SLS / CloudWatch logs.
• Control plane (Mortar Center web UI + the orchestrator) runs on Mortar’s account. Issues credentials, pushes config, reads metadata. Has NO access to customer rows.
• IAM cross-account role — customer creates a mortar-control-plane IAM role that Mortar’s account can assume. Scoped to: manage RDS / OSS / FC / Lambda resources. NOT scoped to: read row data, decrypt KMS keys, modify IAM.
• Lower margin but unlocks contracts that require data residency in the customer’s account.

What lives where

┌─────────────────────────────────┐    ┌─────────────────────────────────┐
│  Mortar's AWS account           │    │  Customer's AWS account         │
│                                 │    │                                 │
│  ┌───────────────────────────┐  │    │  ┌───────────────────────────┐  │
│  │  Mortar Center web UI     │  │    │  │  RDS Postgres (data)       │  │
│  │  Mortar orchestrator      │ ─┼────┼─▶│  S3 buckets (data)         │  │
│  │  Mortar billing service   │  │ as │  │  ElastiCache (cache)        │  │
│  │  Audit aggregator         │  │sume│  │  Lambda (compute)           │  │
│  └───────────────────────────┘  │role│  │  CloudWatch Logs            │  │
│                                 │    │  │  Mortar binary (data plane) │  │
│  ┌───────────────────────────┐  │    │  └───────────────────────────┘  │
│  │  Aggregated usage metrics │ ◀┼────┼─ (CloudWatch metric streams)    │
│  └───────────────────────────┘  │    │                                 │
└─────────────────────────────────┘    └─────────────────────────────────┘

Customer account (data plane)

• RDS PostgreSQL — Mortar’s primary DB. Customer chooses size, storage class, encryption settings.
• S3 buckets — file storage. Customer KMS keys.
• ElastiCache (Redis) — cache + rate-limit counters.
• Lambda functions — user-deployed compute. Customer’s IAM execution role.
• CloudWatch Logs — function output + audit-event stream.
• EC2 / EKS — runs the Mortar binary itself (auto-deployed by the orchestrator).

Mortar account (control plane)

• Mortar Center — the web UI + tenant management. No customer data; only metadata (which customer, what tier, what region).
• Orchestrator — issues commands to the data plane through the cross-account role. Stateless; redeploys without touching customer state.
• Billing — sums usage metrics, generates invoices.
• Audit aggregator — pulls aggregate metric streams (per-customer request counts, ledger entries, etc.); never raw rows.

IAM setup

Customer creates a cross-account IAM role in their AWS account:

# mortar-control-plane.tf
resource "aws_iam_role" "mortar_control_plane" {
  name = "mortar-control-plane"
  assume_role_policy = jsonencode({
    Version = "2012-10-17"
    Statement = [{
      Effect = "Allow"
      Principal = { AWS = "arn:aws:iam::<MORTAR_ACCOUNT_ID>:root" }
      Action = "sts:AssumeRole"
      Condition = {
        StringEquals = { "sts:ExternalId" = "<CUSTOMER_TENANT_ID>" }
      }
    }]
  })
}

resource "aws_iam_role_policy" "mortar_control_plane" {
  role = aws_iam_role.mortar_control_plane.id
  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      # Provision + tear down Mortar's data-plane resources.
      { Effect = "Allow", Action = "rds:*",         Resource = "*" },
      { Effect = "Allow", Action = "s3:*",          Resource = "arn:aws:s3:::mortar-*" },
      { Effect = "Allow", Action = "elasticache:*", Resource = "*" },
      { Effect = "Allow", Action = "lambda:*",      Resource = "*" },
      { Effect = "Allow", Action = "logs:*",        Resource = "*" },
      # Provision the Mortar binary host.
      { Effect = "Allow", Action = "ec2:*",         Resource = "*" },
      { Effect = "Allow", Action = "ecs:*",         Resource = "*" },
      # Read aggregate metrics for billing.
      { Effect = "Allow", Action = "cloudwatch:GetMetricStatistics", Resource = "*" },
      { Effect = "Allow", Action = "cloudwatch:ListMetrics",         Resource = "*" },
    ]
  })
}

External ID is mandatory — prevents the confused-deputy attack where one Mortar customer’s tenant ID is used to assume role into a different customer’s account.

What we deliberately exclude from the policy:

• kms:Decrypt — Mortar can’t decrypt customer KMS keys; data stays customer-readable only.
• iam:* — Mortar can’t elevate its own privileges or create new cross-account roles.
• rds:Modify*Tags / Add*Permission on the actual database — we manage Postgres metadata but never run arbitrary SQL.

The Aliyun equivalent is RAM cross-account roles (AssumeRole); same shape, different syntax.

Bootstrap flow

1. Customer signs up via Mortar Center, picks “BYOC” deployment.
2. Customer pastes their AWS account ID; Mortar Center generates an External ID + Terraform module.
3. Customer applies the Terraform. IAM role created in their account.
4. Customer pastes the IAM role ARN back to Mortar Center.
5. Orchestrator assumes the role + provisions:
   • VPC + security groups
   • RDS Postgres (single-AZ for dev, Multi-AZ for prod tier)
   • S3 buckets (mortar-files-<tenant>-<random>, etc.)
   • ElastiCache cluster
   • EC2 / ECS instance running the Mortar binary
6. Orchestrator writes the binary’s MORTAR_* env-vars from the provisioned endpoints. Customer’s Mortar boots and registers with Mortar Center.
7. Customer adds their domain to Mortar Center; CNAME points at the customer-account Mortar.

Tear down: customer revokes the IAM role. Orchestrator can no longer operate; customer’s existing infrastructure keeps running until they manually delete it. No “abandoned by Mortar” failure mode — the binary is statelessly configured + customer-owned.

Pricing impact

BYOC customers pay Mortar Center fees + their own AWS bill. No metered Cloud credits from Mortar — the customer’s cloud spend is the metered usage.

Lower margin than hosted Mortar Cloud (we don’t markup the cloud bill), but unlocks deals we’d otherwise lose entirely:

• Banks — every domestic state-owned bank insists on data not leaving their VPC / their data center. BYOC + Sovereign tier closes those.
• Hospitals — HIPAA / PIPL-medical equivalent require named control over data location.
• Fortune 500 R&D — proprietary trade-secret data; legal won’t approve hosted Mortar at any price.
• Government — government / enterprise customers, especially in regulated industries (electricity, telecoms), require sovereignty over the data path.

Cloud support matrix

Pilot acceptance criteria

• Cross-account role Terraform module published.
• Orchestrator assumes role + provisions RDS / S3 / ElastiCache / Lambda end-to-end against a fixture customer account.
• Bootstrap flow walks through Mortar Center without manual ops.
• Billing pulls CloudWatch metrics + invoices the per-tenant total.
• First paying BYOC pilot signed.