capability
verified July 2026
Burst lines: capacity priced by the day.
Every voice fleet has two sizes: the ordinary day and the spike. Committed lines price the first; burst lines price the second — $10 a line-day, only on the days the spike is real, with a cap you set.
01
The mechanics
- Traffic past your committed lines spills over automatically — callers hear an answer, not a busy signal.
- Each burst line bills $10 for that day only; a quiet day bills nothing.
- The dashboard cap is the control: set the maximum burst line-days you will accept, and past cap the API refuses fast with a retryable 503 instead of surprising finance.
02
The break-even, stated
Fig. — Burst vs committed — the crossing
15 days
spike days a month where burst spend matches a committed line
$10 × days
the whole burst formula — nothing else moves
A line that spikes three days a month costs $30 on burst against $150 committed. Past fifteen spike days, the honest move is another committed line — the dashboard cap makes that conversation happen on numbers.
Table 1 — One overflow line, priced both ways
| Spike days / mo | On burst | A committed line |
|---|---|---|
| 3 | $30 | $150 |
| 10 | $100 | $150 |
| 15 | $150 | $150 · break-even |
| 22 | $220 | $150 |
03
Where burst earns its keep
The workloads that spike by calendar, not by trend: the 8 AM Monday wave on a front desk, the 9 AM reminder window, the end-of-quarter dialer push, catastrophe morning on a claims line, peak season on order status. Each of those pages does its own arithmetic; this page is the mechanism they all lean on.
04
Notes — an engineer's checklist
01Do I have to enable burst?
It is a dashboard cap: set it to zero and traffic past your lines gets the retryable 503 instead of spilling. Set it high for storm season, low for the quiet quarter — the knob is yours.
02Is a burst line slower than a committed line?
No — a burst line is the same serving path with the same measured figures. Burst is a billing state, not a serving tier.
03How do I know how many burst days I used?
Burst activations are visible in the dashboard, and each workload’s traffic remains auditable on its own key at GET /v1/usage — so the spike that caused the spend is identifiable, not a mystery line item.
See also
Related sheets.
glossary
1 line
Concurrent lines
A line is one simultaneous conversation. Why concurrency — not minutes — is the real capacity unit for voice agents, and how metered plans cap it quietly.
use case
2,000
TTS for insurance claims calls
Claims lines are quiet until catastrophe day. Sizing voice capacity for the storm with burst lines, long structured turns, and one cloned voice in 23 languages.
use case
2,000 min
TTS for appointment reminders and notifications
Reminder traffic is bursty and short-form. Where a meter genuinely wins, this page says so — and where burst lines beat both, it shows the arithmetic.
capability
3 tiers
Serving that degrades before it fails
Three serving tiers behind one endpoint — primary GPU fleet, warm spill, independent fallback — and a fast retryable 503 past absolute capacity.
Your script, this API, thirty minutes — and the recording leaves with you.
Hear it on your own script