2nd/10_Wiki/Topic_Programming/Architecture/Single_Source_of_Truth.md

id, title, category, status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, verification_status, tags, raw_sources, last_reinforced, github_commit, tech_stack

id	title	category	status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	verification_status	tags	raw_sources	last_reinforced	github_commit	tech_stack
wiki-2026-0508-single-source-of-truth	Single Source of Truth (SSoT)	10_Wiki/Topics	verified	self	SSoT Single Source of Truth Authoritative Source	none	A	0.9	applied	architecture data principle consistency		2026-05-10	pending	language framework typescript redux

Single Source of Truth (SSoT)

매 한 줄

"매 fact 의 1 authoritative location. Everywhere else 의 derive.". 매 information architecture 의 fundamental principle — duplication 의 minimize 후 매 derived view 의 cache/projection 으로 처리. 매 frontend (Redux), backend (master DB), DevOps (Git as IaC source) 의 cross-cutting pattern.

매 핵심

매 layers

• DB layer: master DB + read replicas (no parallel sources).
• App state: Redux store / TanStack Query cache.
• Config: Git repo (Infrastructure as Code).
• Identity: SCIM-synced IdP (Okta/Entra).
• Schema: protobuf / OpenAPI as type-source.

매 derived view

• Materialized views (DB).
• Selectors / memoized derive (frontend).
• Search indexes (Elastic) reflecting master.
• Reporting cubes built from master.

매 응용

1. Redux Toolkit createSlice — 1 store, derived UI.
2. Git → Terraform → Cloud (no console drift).
3. SCIM provisioning — IdP authoritative.
4. CDC (Debezium) — master DB → downstream consumers.
5. Event sourcing — log as SSoT.

💻 패턴

Redux normalize + selector

import { createSlice, createSelector } from '@reduxjs/toolkit';

const usersSlice = createSlice({
  name: 'users',
  initialState: { byId: {} as Record<string, User> },
  reducers: { upsert: (state, { payload }) => { state.byId[payload.id] = payload; } },
});

export const selectUser = (id: string) => (state: RootState) => state.users.byId[id];
export const selectActiveUsers = createSelector(
  (s: RootState) => Object.values(s.users.byId),
  (users) => users.filter(u => u.active),
);

Terraform as IaC SSoT

resource "aws_s3_bucket" "logs" {
  bucket = "company-logs-prod"
  tags = { managed_by = "terraform", repo = "infra" }
}
# Console changes drift-detected via `terraform plan`

Debezium CDC

connector.class: io.debezium.connector.postgresql.PostgresConnector
database.hostname: master.db
table.include.list: public.orders
plugin.name: pgoutput
# Master postgres → Kafka → search/analytics consumers

Schema-first (protobuf)

syntax = "proto3";
message User {
  string id = 1;
  string email = 2;
  bool active = 3;
}
// codegen → TS, Go, Python types — single schema source

Materialized view (Postgres)

CREATE MATERIALIZED VIEW user_stats AS
SELECT user_id, COUNT(*) AS orders, SUM(total) AS revenue
FROM orders GROUP BY user_id;

REFRESH MATERIALIZED VIEW CONCURRENTLY user_stats;

SCIM provisioning

// IdP (Okta) → /scim/v2/Users — app receives, never originates user identity
app.put('/scim/v2/Users/:id', (req, res) => {
  await db.upsertUser(req.params.id, req.body);
  res.status(200).json(req.body);
});

TanStack Query cache as derived

const { data: user } = useQuery({
  queryKey: ['user', id],
  queryFn: () => api.getUser(id),
  staleTime: 60_000,
});
// Server is SSoT — cache is derived view with TTL

매 결정 기준

상황	Approach
Cross-system data sync	CDC from master DB
Cloud config	Git + Terraform
User identity	IdP + SCIM
Frontend state	Normalized Redux + selectors
Analytics	Reflect master via warehouse

기본값: master + derived projections — never multi-master unless conflict-resolution strategy defined.

🔗 Graph

• 부모: Data-Modeling
• 변형: Event Sourcing · CQRS
• 응용: Redux-Toolkit · Terraform · CDC · GitOps
• Adjacent: Eventual Consistency

🤖 LLM 활용

언제: design-time data flow review, drift audit, cache invalidation strategy. 언제 X: distributed systems with offline-first requirement — CRDT 가 적합.

❌ 안티패턴

• Dual-write: 매 app writes both DB and search — drift inevitable. CDC 사용.
• Console drift: cloud console change without IaC update.
• Cached as authoritative: TTL stale → cache mistakenly trusted.

🧪 검증 / 중복

• Verified (Fowler, Kleppmann DDIA, Redux docs, Terraform best practices).
• 신뢰도 A.

🕓 Changelog

날짜	변경
2026-05-08	Phase 1
2026-05-10	Manual cleanup — SSoT principle, master + derived patterns, CDC/IaC/SCIM