{
  "checked_on": "2026-11-02",
  "scope": "Primary technical documentation and regulator/vendor public guidance; no corporate deployment claims.",
  "sources": [
    {
      "id": "R4-kafka",
      "title": "Kafka 4.1 design",
      "url": "https://kafka.apache.org/41/design/design/",
      "version_scope": "4.1",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-pgiso",
      "title": "PostgreSQL isolation",
      "url": "https://www.postgresql.org/docs/17/transaction-iso.html",
      "version_scope": "17",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-pglock",
      "title": "PostgreSQL locking",
      "url": "https://www.postgresql.org/docs/17/explicit-locking.html",
      "version_scope": "17",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-pgwal",
      "title": "PostgreSQL asynchronous commit",
      "url": "https://www.postgresql.org/docs/17/wal-async-commit.html",
      "version_scope": "17",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-pgha",
      "title": "PostgreSQL standby",
      "url": "https://www.postgresql.org/docs/17/warm-standby.html",
      "version_scope": "17",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-pitr",
      "title": "PostgreSQL PITR",
      "url": "https://www.postgresql.org/docs/17/continuous-archiving.html",
      "version_scope": "17",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-flink",
      "title": "Flink fault tolerance",
      "url": "https://nightlies.apache.org/flink/flink-docs-release-1.20/docs/learn-flink/fault_tolerance/",
      "version_scope": "1.20.3",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-redis",
      "title": "Redis persistence",
      "url": "https://redis.io/docs/latest/operate/oss_and_stack/management/persistence/",
      "version_scope": "rolling; examples 7.4",
      "access": "WEB_READ",
      "limitations": "Rolling sources require feature verification against deployed baseline; reading is not runtime verification."
    },
    {
      "id": "R4-locks",
      "title": "Redis distributed locks",
      "url": "https://redis.io/docs/latest/develop/clients/patterns/distributed-locks/",
      "version_scope": "rolling; examples 7.4",
      "access": "WEB_READ",
      "limitations": "Rolling sources require feature verification against deployed baseline; reading is not runtime verification."
    },
    {
      "id": "R4-etcd",
      "title": "etcd API guarantees",
      "url": "https://etcd.io/docs/v3.5/learning/api_guarantees/",
      "version_scope": "3.5",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-ch",
      "title": "ClickHouse insert deduplication",
      "url": "https://clickhouse.com/docs/concepts/features/operations/insert/deduplicating-inserts-on-retries",
      "version_scope": "rolling; examples 25.8",
      "access": "WEB_READ",
      "limitations": "Rolling sources require feature verification against deployed baseline; reading is not runtime verification."
    },
    {
      "id": "R4-airflow",
      "title": "Airflow best practices",
      "url": "https://airflow.apache.org/docs/apache-airflow/3.1.0/best-practices.html",
      "version_scope": "3.1.0",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-cdc",
      "title": "Debezium PostgreSQL",
      "url": "https://debezium.io/documentation/reference/3.3/connectors/postgresql.html",
      "version_scope": "3.3",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-retry",
      "title": "AWS timeouts and jitter",
      "url": "https://aws.amazon.com/builders-library/timeouts-retries-and-backoff-with-jitter/",
      "version_scope": "article; accessed 2026-11-02",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-breaker",
      "title": "Circuit Breaker, original description",
      "url": "https://martinfowler.com/bliki/CircuitBreaker.html",
      "version_scope": "2014; conceptual",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-otel",
      "title": "OpenTelemetry signals",
      "url": "https://opentelemetry.io/docs/concepts/signals/",
      "version_scope": "rolling; conceptual",
      "access": "WEB_READ",
      "limitations": "Rolling sources require feature verification against deployed baseline; reading is not runtime verification."
    },
    {
      "id": "R4-schema",
      "title": "Confluent Schema Registry evolution",
      "url": "https://docs.confluent.io/platform/current/schema-registry/fundamentals/schema-evolution.html",
      "version_scope": "rolling; verify installed registry",
      "access": "WEB_READ",
      "limitations": "Rolling sources require feature verification against deployed baseline; reading is not runtime verification."
    },
    {
      "id": "R4-chaos",
      "title": "Principles of Chaos Engineering",
      "url": "https://principlesofchaos.org/",
      "version_scope": "2019-03",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-gdpr",
      "title": "European Commission GDPR principles",
      "url": "https://commission.europa.eu/law/law-topic/data-protection/information-business-and-organisations/principles-gdpr_en",
      "version_scope": "GDPR 2016/679; guidance",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-erasure",
      "title": "Irish DPC: erasure, Articles 17 and 19",
      "url": "https://www.dataprotection.ie/en/individuals/know-your-rights/right-erasure-articles-17-19-gdpr",
      "version_scope": "GDPR 2016/679; regulator guidance",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-pci",
      "title": "PCI SSC: PCI DSS scope",
      "url": "https://www.pcisecuritystandards.org/standards/pci-dss/",
      "version_scope": "public scope overview",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-pciver",
      "title": "PCI SSC: release 4.0.1",
      "url": "https://blog.pcisecuritystandards.org/just-published-pci-dss-v4-0-1",
      "version_scope": "4.0.1; 2024",
      "access": "WEB_READ",
      "limitations": "Documented scope only; no runtime proof."
    },
    {
      "id": "R4-pgindex",
      "title": "PostgreSQL unique index",
      "url": "https://www.postgresql.org/docs/17/sql-createindex.html",
      "version_scope": "17",
      "access": "WEB_READ",
      "limitations": "Uniqueness contract; no runtime proof."
    }
  ],
  "open_questions": [
    "EUR-Lex full GDPR text access blocked by JS verification; regulator/Commission guidance used, no legal completeness claimed.",
    "Full PCI DSS 4.0.1 requirements and entity-specific assessment not verified; public scope and release information only.",
    "ClickHouse rolling docs include newer async insert behavior; not imported as baseline25.8 guarantees."
  ]
}