---
title: "Prompt-cache: what you already save, and what turning it on would save · 0 credits"
method: GET
path: "/api/v1/llm-providers/{id}/cache-projection"
tags: ["BYO-LLM"]
---

# Prompt-cache: what you already save, and what turning it on would save · 0 credits

`GET /api/v1/llm-providers/{id}/cache-projection`

## Request

- Base URL: `https://legal.nexusquantum.legal`
- URL: `https://legal.nexusquantum.legal/api/v1/llm-providers/{id}/cache-projection`
- Auth: HTTP bearer

Answers, on YOUR real traffic and without spending anything, whether explicit prompt caching is worth enabling on this engine. Two figures, deliberately kept apart: `measured` is what already happened, read from telemetry; `projection` is an UPPER BOUND of what explicit caching would have done — provider caches are best effort, Anthropic counts the TTL from the start of the request, and past traffic does not predict a changed pattern. `measured: null` means NOT MEASURED (no calls in the window), which is not the same as zero. `applies:false` on OpenAI-shaped providers is not a limitation: those cache by prefix match automatically, so there is nothing to switch on and `measured` already shows the saving. Traffic is attributed by firm + kind + model (telemetry stores the model, not the config id); when another engine of yours shares both, `attribution_note` says so. No prompt text, no credentials, no fingerprints: counters only. Query: `dias` (1-90, default 30) and `ttl` (`5m` | `1h`). Scope: mcp | * (NOT cases).

## Path parameters

- `id` string, uuid, required

## Query parameters

- `dias` integer
- `ttl` '5m' | '1h'

## Response `200`

Measured usage and, where explicit caching applies, the projection and its recommendation (`activar` | `no-compensa` | `sin-datos`).

## Other responses

- `404`: NOT_FOUND (does not exist or does not belong to your firm)
- `503`: TABLA_SIN_CREAR (prompt-cache telemetry is not available in this environment — this is «could not look», NOT «you save nothing»)

---

[API](https://skmtc.dev/nexusquantum/apis/nexus-legal-api.md) · [All operations](https://skmtc.dev/nexusquantum/apis/nexus-legal-api/llms.txt) · [OpenAPI document](https://skmtc.dev/nexusquantum/apis/nexus-legal-api/revisions/4084d8d4eb0b?raw)