At a glance
- Did you know
- Sandboxes run model-written code in an isolated container with limited network and time.
- Rule of thumb
- Set CPU, memory and wall-clock limits; generated code can loop forever.
- Watch out
- Cold starts; sandbox queueing; timeouts.
Its settings in ScaleMySystems
What you can change on it in the lab, and what each number does.
- Concurrency (slots)
- Calls it can work on at once (per instance when autoscaling). Needed slots ≈ calls per second × seconds each takes. Extra calls wait in the queue, then are rejected.
- Queue capacity
- Calls allowed to wait for a free slot. A bigger queue absorbs bursts but adds waiting time; 0 rejects straight away.
- vCPU
- CPU cores available. Needed ≈ calls per second × CPU per request ÷ 1000. Above about 90% busy it slows down and may crash.
- CPU per request (ms)
- CPU time each call burns. Part of what the component is; make the code cheaper to lower it.
- Latency (p50) (ms)
- Typical time one call takes here, before any calls it makes itself. Slots are held for this long.
- Latency (p99) (ms)
- The slowest 1% of calls. Callers must set their timeout above this or they cut off healthy calls.
- Timeout to dependencies (ms)
- How long it waits for each call it makes before giving up. Set it above the dependency’s p99 but low enough that a dead dependency does not hold every slot.
- Error rate
- Share of calls that fail on their own (bugs, declines, flaky tools). An agent that calls it on every step multiplies this.
- Quota (req/min)
- Calls allowed per minute (an API key or provider limit). Calls over it get 429s. Needed = calls per second × 60, with headroom.
Problems that start with it
- Code sandboxes run out A data-analysis agent runs Python in sandboxes: 6 sandboxes, about 1.2 s per run, 4 runs per task at 2 tasks a second.
- Harness test runs A coding harness runs the test suite in a sandbox every turn. 8 sandboxes, about 1.2 s per run.
- Sandboxes held during approvals A coding-agent platform runs 7 tasks a second with 3 sandbox runs each, about 3.5 s per run, on a provider that allows 100 sandboxes at once. On 30% of runs the sandbox asks a person to approve a command and stays reserved (and billed) while it waits, about 12 s. Times are scaled: a second here stands for a minute.
- Coding agent platform: the model provider goes down A coding agent platform: each task is a loop of model calls, tool calls, code runs in a sandbox and checkpoints, minutes long. Twenty seconds in, the model provider has an outage for 30 seconds. Every step that needs the model fails, and with it the whole task: two in three tasks are lost.
Full lesson coming soon
Lessons are being added one component at a time: how it works, its settings, a live exercise to break and fix it, interview questions and a short check. See the Circuit breaker lesson for what one looks like.