# GRAPHQL Data Simulation > Faking GraphQL responses, schemas, and subscription streams for offline demos without a live server Use when this capability is needed. - Skill: `tomevault-io/graphql-data-simulation` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/graphql-data-simulation` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/graphql-data-simulation/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Integrations & APIs - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/graphql-data-simulation --- # graphql-data-simulation For demo apps that showcase GraphQL tooling, running a real Apollo/Yoga server is overkill and brittle in static hosting. Instead, simulate in three layers. **Schema layer**: ship a hand-written SDL string (or a small JSON introspection dump) as a module export — this is what the schema-graph and query-builder introspect against. Keep it representative (object types, interfaces, unions, enums, input types, custom scalars, `@deprecated`) so every UI branch has something to render. **Query execution layer**: implement a tiny resolver over a seeded in-memory dataset, or a `Map` lookup keyed by the normalized query string. Return results via `Promise.resolve()` wrapped in an artificial `setTimeout` so loading states actually appear. **Subscription layer**: simulate push with `setInterval` emitting synthetic events into an `EventTarget` or RxJS `Subject`, and have the feed component subscribe to that. Vary the cadence (burst of 5 in 200ms, then idle 3s) so backpressure, batching, and deduplication UI behaviors are visible in a demo. Seed event payloads from a small pool with deterministic-but-jittered fields (timestamps `Date.now()`, IDs from a counter, enum values cycled) so the feed looks alive without being random noise. Gate the simulation behind a single `USE_MOCK_GRAPHQL` flag or a `createClient({mode: 'mock' | 'real'})` factory so the same components run against a real endpoint later with zero changes. Keep fixtures colocated with the mock client (`mocks/schema.graphql`, `mocks/fixtures.ts`) — not scattered across components — so updating the demo story is a one-file edit. --- > Source: [kjuhwa/skills-hub](https://github.com/kjuhwa/skills-hub) — distributed by [TomeVault](https://tomevault.io).