How to run SQL queries in a sandbox (SQLite and PostgreSQL)

Run the SQL against a throwaway database inside a Linux microVM: SQLite with the sqlite3 shell, or PostgreSQL installed from apt.

On Runtime SQLite is already in every sandbox, and a full PostgreSQL server is one apt install away. Each sandbox is a Firecracker microVM running Ubuntu 24.04.5 with sqlite3 in the image and passwordless sudo, so a query a model wrote can run against a copy of the data, never your production database. A new sandbox took 351 ms from the create request to its first Python result at the median, measured on 24 September 2026 (speed).

SQLite or PostgreSQL?

Run a query on SQLite

Pass the SQL on stdin and name the database as an argument. With -bail the shell stops at the first error; -json prints rows as JSON for your code to parse (sqlite3 command-line shell).

TypeScriptimport { Sandbox } from "withruntime";const setup = `CREATE TABLE orders(id INTEGER PRIMARY KEY, customer TEXT, total REAL);INSERT INTO orders(customer, total) VALUES ('ada', 30.5), ('bo', 12), ('ada', 7.25);`;const query =  "SELECT customer, SUM(total) AS spent FROM orders GROUP BY customer ORDER BY spent DESC;";await using sbx = await Sandbox.create({  network: { internet: false },  timeoutSeconds: 300,  onLeaseEnd: "stop",});await sbx.exec(["sqlite3", "-bail", "shop.db"], { stdin: setup, check: true });const rows = await sbx.exec(["sqlite3", "-bail", "-safe", "-json", "-readonly", "shop.db"], {  stdin: query,  timeoutMs: 30_000,});console.log(rows.exitCode, rows.stdout); // [{"customer":"ada","spent":37.75}, ...]

Pythonfrom withruntime import Sandboxsetup = """CREATE TABLE orders(id INTEGER PRIMARY KEY, customer TEXT, total REAL);INSERT INTO orders(customer, total) VALUES ('ada', 30.5), ('bo', 12), ('ada', 7.25);"""query = "SELECT customer, SUM(total) AS spent FROM orders GROUP BY customer ORDER BY spent DESC;"with Sandbox.create(network={"internet": False}, timeout_seconds=300, on_lease_end="stop") as sbx:    sbx.exec(["sqlite3", "-bail", "shop.db"], stdin=setup, check=True)    rows = sbx.exec(["sqlite3", "-bail", "-safe", "-json", "-readonly", "shop.db"], stdin=query, timeout_ms=30_000)    print(rows.exit_code, rows.stdout)

Three flags make the shell safer for SQL you did not write:

• -readonly opens the database read-only.
• -safe turns off every shell feature that reads or writes a file other than the database: ATTACH, readfile(), writefile(), load_extension(), .shell, .system, .import, .output and more.
• timeoutMs ends a runaway query from outside; the result says timedOut: true.

To query your own data, upload the database file with sbx.files.write or a folder with sbx.files.upload, and download the changed file after.

Run PostgreSQL in the sandbox

Ubuntu's postgresql package creates a cluster named 16/main. Start it with pg_ctlcluster, which needs no service manager, and create a role for the sandbox user so psql connects over the local socket without a password.

TypeScriptimport { Sandbox } from "withruntime";await using sbx = await Sandbox.create({ timeoutSeconds: 1800, onLeaseEnd: "stop" });const slow = { check: true, timeoutMs: 600_000 } as const;await sbx.exec("sudo apt-get update -q && sudo apt-get install -y -q postgresql", slow);await sbx.exec("sudo pg_ctlcluster 16 main status || sudo pg_ctlcluster 16 main start", slow);await sbx.exec(  "sudo -u postgres createuser --superuser runtime && createdb -O runtime runtime",  slow,);await sbx.network.set({ internet: false });await sbx.files.write(  "/workspace/check.sql",  "CREATE TABLE t(n int); INSERT INTO t SELECT generate_series(1, 1000); SELECT count(*), sum(n) FROM t;",);const run = await sbx.exec(["psql", "-v", "ON_ERROR_STOP=1", "-At", "-f", "check.sql"], {  timeoutMs: 60_000,});console.log(run.exitCode, run.stdout); // 1000|500500

Pythonfrom withruntime import Sandboxwith Sandbox.create(timeout_seconds=1800, on_lease_end="stop") as sbx:    sbx.exec("sudo apt-get update -q && sudo apt-get install -y -q postgresql", check=True, timeout_ms=600_000)    sbx.exec("sudo pg_ctlcluster 16 main status || sudo pg_ctlcluster 16 main start", check=True)    sbx.exec("sudo -u postgres createuser --superuser runtime && createdb -O runtime runtime", check=True)    sbx.network.set(internet=False)    run = sbx.exec(["psql", "-v", "ON_ERROR_STOP=1", "-At", "-c", "SELECT version();"], timeout_ms=60_000)    print(run.exit_code, run.stdout)

ON_ERROR_STOP=1 makes psql stop at the first failing statement and exit non-zero, so a broken migration fails the command. The network rule refuses connections out of the sandbox; localhost inside it keeps working.

Start every sandbox with Postgres running

An image can install PostgreSQL and say how a sandbox starts it. The create call answers once port 5432 is listening (start and ready commands):

TypeScriptimport { Runtime } from "withruntime";const runtime = new Runtime();await runtime.images.build({  name: "postgres",  recipe: { apt: ["postgresql"] },  start: {    command: "sudo pg_ctlcluster 16 main start && sleep infinity",    readyPort: 5432,    readyTimeoutSeconds: 60,  },});await using sbx = await runtime.sandboxes.create({  image: "postgres",  network: { internet: false },});console.log(sbx.info.start); // { state: "ready", ... }await sbx.exec("sudo -u postgres psql -c 'SELECT 1'", { check: true });

pg_ctlcluster returns once the server is up, and a start command that ends counts as exited, so sleep infinity keeps it running.

For many test runs against the same seeded data, load it once, then fork the running sandbox: each copy starts with the server up and the data in memory, and nothing one copy writes reaches another.

What it costs

A database that sits idle between queries costs the CPU floor, a twentieth of a vCPU at $0.025 per vCPU-hour, plus memory at $0.0075 per GiB-hour. A 2 vCPU, 4 GiB sandbox costs $0.03125 an hour waiting and $0.08 an hour fully busy (pricing). New accounts get 50 free sandbox hours, no card:

Terminalnpx withruntime sandbox run --trial -- sqlite3 :memory: 'select sqlite_version();'

See also a data analysis agent, agent evals and running untrusted LLM code.

Sources

Checked 25 September 2026.

• SQLite command-line shell: -bail, -json, -readonly, -safe
• Ubuntu 24.04 (noble) packages: sqlite3, postgresql, postgresql-16, postgresql-common file list (pg_ctlcluster)

Facts on this page were checked on 25 September 2026.