Data Lake Starter — A Secure Home for All Your Business Data

Start here. This is the first skill in the foundation tier. It builds the secure, empty lake that every other skill in this kit reads from and writes to.

How to use this skill

Don't run these steps by hand. Hand them to an AI agent and let it drive.

This skill is written to be run by an agent on your behalf — Claude Code or Claude Desktop — not copy-pasted into a terminal by you. That's not just easier; it's how the lake gets set up securely: the agent runs each gcloud / terraform command with judgment, explains every security choice as it goes, checks its own work, and never writes a secret to disk.

Getting started (about 5 minutes):

1. Install an agent. Claude Desktop is the no-terminal option; Claude Code is the CLI version.
2. Add this skill. Clone the kit and copy this folder into your agent's skills directory:

   git clone https://github.com/pbc-os/smb-starter-kit.git
   cp -r smb-starter-kit/skills/tier-1-foundation/data-lake-starter ~/.claude/skills/data-lake-starter

   (Not comfortable with git? Download the repo as a ZIP from GitHub and copy the folder. On Windows the skills directory is %APPDATA%\Claude\skills\.)
3. Ask the agent to run it. Open the agent and say: "Use the data-lake-starter skill to build my data lake — walk me through it."

New to all of this? Start with the repo README. The rest of this document is written for the agent — you're welcome to read along, but you don't have to run anything yourself.

1. The Vision: You Already Have the Data

Every small business is already generating enterprise amounts of data. Your POS, your accounting, your email tool, your ad accounts, your reviews — each one is quietly piling up thousands of rows about your business. The problem was never having the data. It's that the data lives in twenty different tools that don't talk to each other, and stitching it together used to require a data team only big companies could afford.

┌──────────────────────── BEFORE: data scattered by design ───────────────────────┐
│                                                                                  │
│   [Square]   [Stripe]   [QuickBooks]   [Google Ads]   [Mailchimp]   [Reviews]    │
│      │           │           │             │              │             │        │
│      ▼           ▼           ▼             ▼              ▼             ▼        │
│   locked      locked      locked        locked         locked        locked      │
│                                                                                  │
│   You can see each one alone. You can never ask a question across all of them.   │
└──────────────────────────────────────────────────────────────────────────────────┘

┌──────────────────────── AFTER: one secure lake you own ──────────────────────────┐
│                                                                                  │
│   [Square]  [Stripe]  [QuickBooks]  [Google Ads]  [Mailchimp]  [Reviews]         │
│      └─────────┴───────────┴─────────────┴─────────────┴───────────┘             │
│                                  │  (you connect these — see §8)                  │
│                                  ▼                                                │
│                       ┌──────────────────────┐                                   │
│                       │   YOUR DATA LAKE      │   one place, your cloud account   │
│                       │   (BigQuery, secured) │   query it in plain English       │
│                       └──────────────────────┘                                   │
│                                                                                  │
│   "How did each location do last weekend vs the same weekend last year?"  ✓      │
│   "Which ads actually drove repeat customers?"                            ✓      │
└──────────────────────────────────────────────────────────────────────────────────┘

This skill builds the lake on the right — empty, secured, and yours. It does not connect your sources (that's your deliberate, manual step — and it's a feature, see §8). It gives your agent a safe place to put data and a safe way to read it back.

2. What This Builds

A clean, layered BigQuery data lake with a one-way flow and a hard wall between raw data and whatever reads it:

                 you connect sources (§8)
                          │
                          ▼
   ┌───────────┐    ┌───────────┐    ┌───────────┐    ┌───────────┐
   │   raw     │──► │   clean   │──► │   marts   │    │  archive  │
   │ landing   │    │ normalized│    │ analytics │    │ retired   │
   │ (has PII) │    │           │    │  (views)  │    │  tables   │
   └───────────┘    └───────────┘    └───────────┘    └───────────┘
        ▲                ▲                 │
        │                │                 │ read-only, via authorized views
   ingest SA        transform SA       agent SA  ◄── your AI agent + dashboards
   (write raw)     (raw→clean→marts)  (reads marts only — never touches raw)

Everything follows the SMB Data Lake Hardening Standard — the security baseline is the whole point.

3. Two Paths (pick one)

Path A gets you the datasets, identities, and project-level roles by hand; Path B additionally applies the dataset-scoped data roles and authorized-view wiring precisely (those are fiddly to do by hand) and is recommended for production. Both enforce the same hardening standard.

4. Prerequisites

• A Google Cloud account with a billing account attached. (No GCP account yet? Ask the agent — it'll walk you through console.cloud.google.com and the free-tier signup. BigQuery's free tier covers a typical SMB; see cost.md.)
• A dedicated GCP project for the lake. One project, one purpose — don't share it with other apps. Create one and set it:

  export GCP_PROJECT_ID="your-lake-project-id"
  gcloud config set project "$GCP_PROJECT_ID"

• gcloud + bq CLIs authenticated. Both ship with the Google Cloud SDK. For Path A run gcloud auth login; for Path B also run gcloud auth application-default login — Terraform authenticates via Application Default Credentials, which is separate from the gcloud CLI login.
• For Path B only: Terraform ≥ 1.5. Tip: export TF_VAR_project_id="$GCP_PROJECT_ID" to reuse the same project value as Path A.

Working With the User — Transparency & Consent

Read this before running anything in Path A or Path B. It is not optional.

This skill creates real resources in the user's own cloud project — some of which cost money (enabling billable APIs, the budget) or grant access (service accounts, IAM). The agent must never make those changes silently.

• Announce before you act. Before each group of changes — enabling APIs, creating datasets, creating service accounts, granting IAM, attaching the budget, configuring Workload Identity — tell the user in plain language what you're about to create, in which project, and why. Name the exact resources.
• Surface the implications. Cost: enabling APIs and the budget touch billing — point the user at cost.md and state the expected range. Access: each IAM grant hands an identity power — say which service account gets which role on which dataset (and that lake-agent stays read-only on marts). Reversibility: datasets are created empty and protected from deletion, but identities and IAM grants persist until you remove them.
• Pause for explicit approval. After announcing a consequential group, stop and ask the user to confirm before running it. Don't act on an earlier blanket "go ahead" — re-confirm at each create / enable / grant. Never run a billing-incurring, access-granting, or destructive command silently.
• Prefer dry-runs. Use terraform plan before apply, and read-only checks before any create.

5. Setup Verification

The agent should confirm these before building:

1. CLI present: which gcloud && which bq
2. Authenticated: gcloud auth list shows an active account
3. Project set & billing linked: gcloud config get-value project and gcloud billing projects describe "$GCP_PROJECT_ID"
4. Caller can administer IAM/BigQuery: the active user needs roles/owner (or bigquery.admin + iam.serviceAccountAdmin + serviceusage.serviceUsageAdmin) on the project

If any check fails, fix it before proceeding — don't build half a lake.

6. Path A — Agent-Guided Build

These are guidance, not a rigid script. Go one step at a time, tell the user what they should see, and adapt commands to their setup. Defaults below: BigQuery location US, dataset prefix lake.

Before each step below, follow Working With the User — Transparency & Consent (above): announce the resources, surface the cost/IAM implications, and get an explicit yes before each create, enable, or grant.

Step 1 — Enable the APIs

gcloud services enable \
  bigquery.googleapis.com secretmanager.googleapis.com \
  cloudresourcemanager.googleapis.com iam.googleapis.com \
  sts.googleapis.com iamcredentials.googleapis.com logging.googleapis.com \
  --project="$GCP_PROJECT_ID"

Step 2 — Create the layered datasets

for ds in raw clean marts archive; do
  bq --location=US mk --dataset \
    --description "Data lake — ${ds} layer" \
    "${GCP_PROJECT_ID}:lake_${ds}"
done

What you should see: four datasets created. raw is your landing zone, marts is what gets read.

Step 3 — Create the three least-privilege service accounts

gcloud iam service-accounts create lake-ingest    --display-name="Data lake — ingest (write raw)"            --project="$GCP_PROJECT_ID"
gcloud iam service-accounts create lake-transform  --display-name="Data lake — transform (raw→clean→marts)"   --project="$GCP_PROJECT_ID"
gcloud iam service-accounts create lake-agent      --display-name="Data lake — agent (read marts only)"       --project="$GCP_PROJECT_ID"

Step 4 — Grant each one the minimum it needs

Everyone needs to run query jobs (project-level), but data access is scoped per dataset:

PID="$GCP_PROJECT_ID"
for sa in lake-ingest lake-transform lake-agent; do
  gcloud projects add-iam-policy-binding "$PID" \
    --member="serviceAccount:${sa}@${PID}.iam.gserviceaccount.com" \
    --role="roles/bigquery.jobUser" --condition=None --quiet
done

Then dataset-scoped data roles (write only where each identity should write). Dataset-level grants are set on the dataset's access list — the agent can patch it via bq update, but Path B (Terraform) does this more precisely and is recommended for the data roles. Intent:

The lake-agent identity — the one your AI agent and dashboards use — can read only marts. It can never touch raw. That wall is the core of the security model.

Step 5 — Turn on audit logging & a budget alert

Audit logging for BigQuery data access, and a billing budget so nothing surprises you. These are fiddly via CLI — let Path B handle them, or follow hardening.md §7 and §9. Confirm with the user either way.

Step 6 — (Recommended) Keyless CI with Workload Identity

If you'll run scheduled ingestion from GitHub Actions or Cloud Run, set up Workload Identity Federation so you never download a service-account key. This is involved — use the wif block in Path B or hardening.md §3.

✅ You now have an empty, secured, layered data lake.

7. Path B — Terraform

Everything above, codified and reproducible. Run terraform plan first, show the user the plan, and get explicit approval before terraform apply.

cd templates/terraform
cp terraform.tfvars.example terraform.tfvars   # then edit: project_id, billing_account, github_repo
terraform init
terraform plan      # read it — it should create datasets, SAs, IAM, audit config, budget
terraform apply

See templates/terraform/README.md for every variable and what each file provisions. The Terraform is the source of truth for the dataset-scoped IAM and authorized views — the parts that are awkward to do by hand.

8. Now Connect Your Sources — On Purpose

The lake is built and empty. Filling it is your job, and it's meant to be.

This kit ships no pre-baked connectors. Not because it's hard — because every credential you mint is a trust decision only you should make. A skill that auto-connected your Square account would need your Square keys; the secure pattern is the opposite — you create each credential at the smallest scope, you store it in your vault, and you decide what gets ingested. That deliberate step is the security boundary, and it stays manual by design.

The secure connection pattern (per source):

1. Mint a credential in the source app  →  least scope, read-only where possible
2. Store it in Secret Manager           →  see the secrets-manager skill (next)
3. Grant lake-ingest access to it        →  one secret, one grant
4. Write a small job that lands the data →  into lake_raw, nothing else
5. Schedule it                           →  Cloud Scheduler / cron

Full walkthrough + a per-source checklist: connecting.md.

9. Cost

A secured lake at SMB scale runs for roughly the price of a coffee per month — often $0 inside the free tier. Honest math, what's free, and when you'd pay more: cost.md.

10. What's Next — Climb the Tiers

You've laid the foundation. The rest of the kit builds on it:

data-lake-starter  ──►  secrets-manager  ──►  (you connect sources, §8)  ──►  semantic-layer-audit
   (this skill)          store your keys        fill the lake                  catalog what's in it
        │
        └──►  then Tier 2 (comms) · Tier 3 (ops) · Tier 4 (growth) · Tier 5 (automation)
              read from the same lake — morning briefings, forecasts, dashboards, and more.

1. secrets-manager — your vault is enabled; now store credentials in it securely.
2. Connect your first source — start with the one you'd most like to query (usually your POS). See connecting.md.
3. semantic-layer-audit — once data is flowing, build a living catalog so your agent always knows what's queryable.
4. Graduate upward — every skill in Tiers 2–5 now has a secure place to read and write.

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