# Category 7 — Performance and Availability (weight 8)

> Because every gateway-mediated tool call routes through the Arcade Engine — even when the custom
> server is self-hosted — Engine latency and availability are a floor on the entire agent stack.
> Verbatim criteria/gates from the criteria Google Doc. Fill Score/Evidence locally; **the human
> pastes**. 1–5 scale; anchors at 1/3/5.

## Scores
| # | Criterion (verbatim) | Score (1–5) | Evidence / note |
|---|---|---|---|
| 1 | Engine-added latency per tool call is within acceptable bounds for interactive agent use. |  |  |
| 2 | Engine SLA — defined uptime guarantees with incident response process. |  |  |
| 3 | Failure behavior when Engine is unavailable: fail-closed with a clean, catchable error. |  |  |
| 4 | Self-hosted server HA — multi-replica, pod failure handling, no dropped calls on restart. |  |  |
| 5 | Multi-region failover design — documented and validated. |  |  |
| 6 | Engine geographic placement and round-trip latency from ServiceTitan's primary region. |  |  |

**Average:** ___   **Category score:** ___

## Score anchors
- **1** — Engine SLA undocumented; failure behavior is a hang or silent failure; no HA guidance
- **3** — SLA documented; HA works with manual configuration; failure behavior is known but requires client-side handling
- **5** — SLA with incident response in writing; HA is the documented default; failure behavior is clean and observable

## Benchmark tests
| # | Test (verbatim) | Result | Evidence |
|---|---|---|---|
| 1 | Make 100 tool calls through the Engine to a self-hosted server. Measure P50, P95, P99 round-trip latency. Compare against a direct server call (bypassing the Engine) to isolate Engine-added overhead. |  |  |
| 2 | Simulate Engine unavailability (block the Engine endpoint). Confirm tool calls fail with a clean, catchable error — not a hang or silent failure. |  |  |
| 3 | Deploy the custom server with multiple replicas. Kill one pod. Confirm tool calls continue without dropped requests. |  |  |
| 4 | Confirm Engine SLA documentation: uptime percentage, response time commitment, and P0 escalation path. |  |  |

## Suggested pass/fail gates
| Gate | Pass condition (verbatim) | Result | Evidence |
|---|---|---|---|
| Engine overhead | P95 Engine-added latency is under 500ms for standard (non-streaming) tool calls |  |  |
| SLA documented | Engine uptime SLA and incident response process confirmed in writing |  |  |
| HA | Self-hosted server survives pod failure; no tool calls dropped during pod restart |  |  |
| Fail behavior | Engine outage produces a clean, catchable error to the agent — no hangs |  |  |

## Findings
-