What is an API latency budget?

It is the allocation of maximum allowable response times across different stages of an API request (like DNS lookup, TLS handshake, and database processing) to meet an overall SLO target.

How does the trace import feature work?

You can paste a JSON trace from OpenTelemetry or Datadog. The tool parses the span durations, groups them by name, and suggests a baseline allocation based on those real measurements.

Why are some stages highlighted in red in the waterfall chart?

Stages that consume more than 35% of the total latency budget are flagged with a red warning to highlight potential performance bottlenecks.

What happens if my allocations exceed the total budget?

The planner displays an over-budget warning, calculates the excess milliseconds, and suggests a proportional reallocation to bring the stages back within the target.

Is my trace data sent to any external servers?

No. All calculations, trace parsing, and waterfall rendering are performed locally in your web browser for complete data privacy.

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API Latency Budget Planner

Plan and visualise an API latency budget. Enter a P99 target (e.g. ≤ 300ms) and per-stage allocations (DNS, TCP, TLS, TTFB, Processing, Network) to see a live waterfall, budget utilisation, and over-budget warnings. Optionally paste an OpenTelemetry or Datadog trace to reverse-engineer a measured allocation.

Details

What this tool helps you do

An SLO / performance-budget planner for SREs and API designers:

Total budget — set the P99 target (e.g. 300ms). Optionally pick a service-level objective label (P50/P90/P99/P99.9) shown in the summary.
Stage allocation — list each request stage and its budgeted milliseconds, one per line, e.g. DNS=5, TLS=20, TTFB=80, Processing=120.
Waterfall — a colour-coded bar chart shows each stage's share of the budget. Stages over a 35% soft cap are flagged red.
Headroom & over-budget — the summary reports how much budget is used and whether you are within or over the target, with a proportional reallocation suggestion.
Trace import — paste an OpenTelemetry or Datadog trace (JSON) and the tool extracts per-span durations, buckets by name, and suggests an initial allocation derived from real measurements.

All computation runs locally in the browser.

Execution

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Prepared example runs

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2 examples

API gateway: 300ms P99 budget

A typical microservice waterfall (DNS, TCP, TLS, TTFB, Processing, Network) inside a 300ms P99 target.

<div class="lp-wrap"><section class="lp-panel lp-summary">…used 275 ms of 300 ms…</section><div class="lp-waterfall">…waterfall bars…</div></div>

Over-budget with trace import

An allocation that exceeds the budget, plus a pasted OpenTelemetry trace that suggests a measured allocation.

<div class="lp-wrap"><section class="lp-summary">…over budget…</section><section><h3>🔬 Measured from trace</h3>…</section></div>

Inputs

Set the required fields, then run the tool.

4 options

ContentPaste or type the main input values.2

Stage allocation (name=ms, one per line)textareaRequiredOne stage per line as name=ms (also accepts name: ms or name ms).Paste trace (OpenTelemetry / Datadog JSON, optional)textareaOptionalOptional OpenTelemetry or Datadog trace JSON. The tool extracts per-span durations to suggest an allocation.

SettingsAdjust formats, ranges, numbers, and modes.2

Total latency budget (P99, ms)numberRequiredThe overall latency target in milliseconds (e.g. 300 for P99 ≤ 300ms).Service-level objectiveselectOptional

Result

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Samples

API Latency Budget Planner

What this tool helps you do

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Key facts

Overview

When to use

How it works

Use cases

Examples

1. Designing a 300ms P99 Budget for a Public API Gateway

2. Diagnosing Latency Budget Overruns via OpenTelemetry Trace

FAQ

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