Runtime

How to run MongoDB in a cloud sandbox

Add MongoDB's apt repository in an Ubuntu 24.04 microVM, install mongodb-org, start mongod with spawn, and load data with mongoimport.

On Runtime, each test or agent gets a MongoDB on a machine of its own. A new sandbox ran its first command 351 ms after the create request at the median on 24 September 2026 (speed); install MongoDB once in an image and every sandbox after that has it on disk, ready for mongod. Each one is a Firecracker microVM with its own kernel, $0.03125 an hour for 2 vCPU and 4 GiB while it waits on queries (pricing).

Where MongoDB comes from

MongoDB is not in Ubuntu's archive: there is no mongodb package for 24.04. MongoDB's install guide, read 25 September 2026, covers MongoDB 8.3 Community Edition and lists Ubuntu 24.04 "Noble" as supported on x86_64, which is what a sandbox runs.

Package What it holds
mongodb-org The meta-package: server, database tools and shell
mongodb-org-server mongod, about 160 MB installed
mongodb-org-tools mongoimport, mongoexport, mongodump and more
mongodb-mongosh mongosh, the shell

The installed size is the one MongoDB's noble repository listed for mongodb-org-server on 25 September 2026. The official Docker image, mongo:8.3, is the other route, with Docker in a sandbox.

Install, start, load, query

TypeScriptimport { writeFile } from "node:fs/promises";import { Sandbox } from "withruntime";const repo = [  "curl -fsSL https://pgp.mongodb.com/server-8.0.asc | sudo gpg -o /usr/share/keyrings/mongodb-server-8.0.gpg --dearmor",  'echo "deb [ arch=amd64,arm64 signed-by=/usr/share/keyrings/mongodb-server-8.0.gpg ] https://repo.mongodb.org/apt/ubuntu noble/mongodb-org/8.3 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-8.3.list',  "sudo apt-get update -qq",  "sudo apt-get install -y -qq mongodb-org",].join(" && ");await using sbx = await Sandbox.create({ diskMiB: 6144, timeoutSeconds: 1800 });await sbx.exec(repo, { check: true, timeoutMs: 600_000 });await sbx.exec("mkdir -p /workspace/db", { check: true });await sbx.spawn("mongod --dbpath /workspace/db --bind_ip 127.0.0.1 --port 27017");await sbx.exec(  "timeout 60 bash -c 'until mongosh --quiet --eval \"db.runCommand({ ping: 1 }).ok\"; do sleep 1; done'",  { check: true, timeoutMs: 90_000 },);await sbx.files.upload("./products.json", "/workspace/products.json");await sbx.exec("mongoimport --db shop --collection products --jsonArray --file products.json", {  check: true,  timeoutMs: 300_000,});const cheap = await sbx.exec(  `mongosh shop --quiet --eval 'db.products.countDocuments({ price: { $lt: 20 } })'`,  { check: true },);console.log("under $20:", cheap.stdout.trim());await sbx.exec("mongoexport --db shop --collection products --out /workspace/out.json", {  check: true,});await writeFile("out.json", await sbx.files.read("/workspace/out.json"));
Pythonfrom withruntime import SandboxREPO = " && ".join([    "curl -fsSL https://pgp.mongodb.com/server-8.0.asc | sudo gpg -o /usr/share/keyrings/mongodb-server-8.0.gpg --dearmor",    'echo "deb [ arch=amd64,arm64 signed-by=/usr/share/keyrings/mongodb-server-8.0.gpg ] '    'https://repo.mongodb.org/apt/ubuntu noble/mongodb-org/8.3 multiverse" '    "| sudo tee /etc/apt/sources.list.d/mongodb-org-8.3.list",    "sudo apt-get update -qq",    "sudo apt-get install -y -qq mongodb-org",])with Sandbox.create(disk_mib=6144, timeout_seconds=1800) as sbx:    sbx.exec(REPO, check=True, timeout_ms=600_000)    sbx.exec("mkdir -p /workspace/db", check=True)    sbx.spawn("mongod --dbpath /workspace/db --bind_ip 127.0.0.1 --port 27017")    sbx.exec("timeout 60 bash -c 'until mongosh --quiet --eval \"db.runCommand({ ping: 1 }).ok\"; "             "do sleep 1; done'", check=True, timeout_ms=90_000)    sbx.files.upload("products.json", "/workspace/products.json")    sbx.exec("mongoimport --db shop --collection products --jsonArray --file products.json",             check=True, timeout_ms=300_000)    print(sbx.exec("mongosh shop --quiet --eval 'db.products.countDocuments({ price: { $lt: 20 } })'",                   check=True).stdout)    sbx.exec("mongoexport --db shop --collection products --out /workspace/out.json", check=True)    sbx.files.download("/workspace/out.json", "out.json")
  • The key and repository lines are MongoDB's own for noble, including its key file name, server-8.0.asc, for the 8.3 repository.
  • mongod runs as the sandbox user with its data in /workspace/db, so it needs no sudo, and spawn keeps it running after the call returns.
  • The repository is served over HTTPS on port 443, which the free trial reaches.

Hand an agent a database it can wreck

A model that writes queries or migrations gets things wrong, sometimes destructively. Run its code in the same sandbox, with the internet off once MongoDB is installed, and a bad deleteMany({}) costs one sandbox:

TypeScriptimport { Sandbox } from "withruntime";declare const db: Sandbox; // the sandbox above, data loadeddeclare const agentScript: string; // the query the model wroteawait db.network.off(); // the model's code can reach nothing outsideawait db.files.write("/workspace/agent.js", agentScript);const result = await db.exec("mongosh shop --quiet --file agent.js", { timeoutMs: 120_000 });console.log(result.exitCode, result.stdout.slice(0, 2000));

Network rules are enforced on the host, so root in the sandbox cannot turn them back on. To give each attempt a fresh copy of the loaded data, fork the sandbox before running it (sandbox fork).

Open it in Compass

Terminalruntime sandbox port-forward <id> 27017

Connect Compass, or your app, to mongodb://127.0.0.1:27017/?directConnection=true. The forward runs through Runtime's API with your key, on the free trial too, and the sandbox opens no port to the internet (forward ports). From code, sbx.forwardPort(27017) or sbx.forward_port(27017) does the same.

Start every sandbox with MongoDB installed

Recipe commands run as root, so the repository lines drop their sudo:

TypeScriptimport { Runtime } from "withruntime";const runtime = new Runtime();await runtime.images.build({  name: "mongodb",  recipe: {    commands: [      "curl -fsSL https://pgp.mongodb.com/server-8.0.asc | gpg -o /usr/share/keyrings/mongodb-server-8.0.gpg --dearmor",      'echo "deb [ arch=amd64,arm64 signed-by=/usr/share/keyrings/mongodb-server-8.0.gpg ] https://repo.mongodb.org/apt/ubuntu noble/mongodb-org/8.3 multiverse" > /etc/apt/sources.list.d/mongodb-org-8.3.list',      "apt-get update && apt-get install -y mongodb-org",    ],  },});await using sbx = await runtime.sandboxes.create({ image: "mongodb" });

Building is free and uses no trial hours; the free trial stores three images free (custom images).

Sizing

  • Disk. The server alone is about 160 MB installed, plus the tools, the shell and your data. The default 4 GiB disk had about 2.5 GiB free on 24 September 2026; the samples ask for 6 GiB, and the trial allows 10.
  • Memory. MongoDB's cache lives in the sandbox's memory, which is what you ask for with memoryMiB and is billed at $0.0075 a GiB-hour while running.
  • Keeping data. A pause keeps the running mongod and its memory. For a disk that outlives sandboxes, put --dbpath on a volume.

For relational data, see PostgreSQL in a sandbox and MySQL in a sandbox.

Sources

Facts on this page were checked on 25 September 2026.

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