ydb-core

name: ydb-core description: Entry point and router for YDB-related work. Orients an LLM about YDB — what it is, what surfaces it exposes, where to read upstream docs, which specialist skill to load for surface-specific questions. Covers SDK packages, connection strings and auth, local Docker, schema fundamentals, common integrations (ORMs, migration tools, Terraform), client-side balancing, and session lifecycle / resilience under rolling restart. Use when the user asks a general YDB question, mentions YDB without naming a specific surface (queries, topics, coordination), needs setup help, asks about balancing policies or BAD_SESSION / shutdownHint / rolling restart, or when another YDB skill needs foundational context. Also triggers on grpcs:// / grpc://, ydb profile, ydb scheme, balancers.RandomChoice, balancers.PreferNearestDC, ydb.WithBalancer, session-balancer, and "getting started with YDB" prompts.

YDB Core

Orientation + router for YDB. Always loaded when the skill fires.

overview

YDB — open-source distributed SQL DBMS. Repo: https://github.com/ydb-platform/ydb. Docs: https://ydb.tech/docs/en/ (source in repo under ydb/docs/ — read from there if the rendered site lags).

All four below live in one database namespace as schema objects — path-addressable (/db/path/to/x), listable via ydb scheme ls:

• Table — rows. SQL (dialect: YQL; say "SQL" in conversation).
• Topic — persistent ordered message stream; queue-like delivery to multiple subscribers. A Kafka-protocol endpoint is exposed so standard Kafka clients work — but the topic itself is a YDB schema object, not a separate service.
• Coordination node — holds semaphores / mutexes / leader-election primitives. Ephemeral semaphores are session-bound: session dies ⇒ lock silently released. Biggest pitfall.
• Changefeed — attached to a table, emits row changes into a topic. Not a webhook.

Don't invent concrete strings (env var names, CLI flags, method signatures, YQL built-ins, config keys). Either take from this file or fetch from docs. Extrapolating from PostgreSQL / MySQL / generic SQL is the #1 source of wrong YDB advice. If the linked page below doesn't answer, say so and quote the link.

Where to read what:

• SQL / YQL syntax → https://ydb.tech/docs/en/yql/reference/
• Concepts (architecture, transactions, MVCC, data model) → https://ydb.tech/docs/en/concepts/
• Glossary → https://ydb.tech/docs/en/concepts/glossary
• SDK guides per language → https://ydb.tech/docs/en/reference/ydb-sdk/
• CLI → https://ydb.tech/docs/en/reference/ydb-cli/

versioning

• Server: CalVer. Current stable at https://github.com/ydb-platform/ydb/releases.
• SDKs version independently per language. Don't assume SDK version tracks server version.

surfaces

Router to specialist skills:

Cluster operations (deployment beyond local, monitoring, backups, capacity) are out of scope of this repo.

packages

SDKs, all official under https://github.com/ydb-platform/:

Q = queries, T = topics, C = coordination.

JDBC driver (separate from Java SDK): https://github.com/ydb-platform/ydb-jdbc-driver, Maven tech.ydb.jdbc:ydb-jdbc-driver. Gateway for JPA/Hibernate/Flyway/Liquibase.

Kafka clients: YDB does NOT ship a Kafka adapter package. Use standard Apache Kafka clients (kafka-clients, franz-go, confluent-kafka-python, kafkajs) against the YDB Kafka endpoint on port 9092. Docs: https://ydb.tech/docs/en/reference/kafka-api/.

CLI (ydb binary): install https://ydb.tech/docs/en/reference/ydb-cli/install. Admin / namespace subcommands (covered here): ydb profile …, ydb discovery …, ydb scheme …. Query execution (ydb sql, ydb yql) — route to the ydb-table skill.

connecting

Connection string shape:

grpcs://<host>:2135/?database=/path/to/db
# or split form:
ydb -e grpcs://<host>:2135 -d /path/to/db ...

grpcs:// — TLS, for anything shared or in production (default port 2135). grpc:// — plaintext, only for local dev (the local Docker image exposes plaintext on port 2136). Suggesting grpc:// for a hosted endpoint is broken advice.

Auth env vars (canonical reference: https://ydb.tech/docs/en/reference/ydb-sdk/auth; verified against ydb-platform/ydb-go-sdk-auth-environ/env.go):

• YDB_SERVICE_ACCOUNT_KEY_FILE_CREDENTIALS — path to a service-account JSON key file.
• YDB_SERVICE_ACCOUNT_KEY_CREDENTIALS — the key itself (raw content, not a path).
• YDB_METADATA_CREDENTIALS — cloud VM / serverless instance metadata service.
• YDB_ACCESS_TOKEN_CREDENTIALS — raw IAM/OAuth access token.
• YDB_OAUTH2_KEY_FILE — OAuth2 key file.
• YDB_STATIC_CREDENTIALS_USER + YDB_STATIC_CREDENTIALS_PASSWORD + YDB_STATIC_CREDENTIALS_ENDPOINT — static user/password auth.
• YDB_ANONYMOUS_CREDENTIALS — local Docker only. Value semantics differ per SDK; check the auth doc.

balancing

Client-side balancer defaults, session lifecycle, shutdownHint / BAD_SESSION behaviour under rolling restart: references/balancing.md, references/session-lifecycle.md.

local-deployment

Single-node docker (https://ydb.tech/docs/en/quickstart):

docker run -d --rm --name ydb-local -h localhost \
  --platform linux/amd64 \
  -p 2135:2135 -p 2136:2136 -p 8765:8765 -p 9092:9092 \
  -v $(pwd)/ydb_certs:/ydb_certs -v $(pwd)/ydb_data:/ydb_data \
  -e GRPC_TLS_PORT=2135 -e GRPC_PORT=2136 -e MON_PORT=8765 \
  -e YDB_KAFKA_PROXY_PORT=9092 \
  ydbplatform/local-ydb:latest

Ports: 2135 gRPCS, 2136 gRPC, 8765 UI/mon, 9092 Kafka-proxy. Connection: grpc://localhost:2136/local or grpcs://localhost:2135/local (database path is /local).

Multi-node dev: Kubernetes Operator (https://github.com/ydb-platform/ydb-kubernetes-operator) or Ansible (https://github.com/ydb-platform/ydb-ansible). No supported Docker Compose multi-node recipe — don't recommend that path.

integrations

Official under https://github.com/ydb-platform/ unless noted.

• Python: SQLAlchemy dialect ydb-sqlalchemy (PyPI). URL scheme: yql+ydb://localhost:2136/local.
• Go: GORM driver gorm-driver; golang-migrate fork with a ydb driver.
• JVM: JDBC driver (see packages) is the gateway. ydb-java-dialects monorepo contains Hibernate 5/6, Spring Data JDBC, JOOQ, Liquibase, Flyway modules. Native ORM yoj-project for immutable entities.
• Spark: ydb-spark-connector.
• Terraform:
  • Schema objects (tables, indexes, changefeeds) inside a YDB database — terraform-provider-ydb (experimental).
  • Yandex Cloud Managed YDB provisioning — yandex-cloud/terraform-provider-yandex (yandex_ydb_database_serverless / _dedicated / _iam_binding, yandex_ydb_table).

Yandex Cloud Managed YDB uses the same engine and same open-source SDKs; only endpoint and IAM-based auth differ. Docs: https://yandex.cloud/en/docs/ydb/.

schema-basics

Dominant LLM failure modes when generating YDB schemas:

• Monotonic first-column PK → hot partition. Common trigger: porting PostgreSQL SERIAL / AUTO_INCREMENT or a plain timestamp. First PK column determines partition; writes to a monotonic key concentrate on one tablet = one CPU. Use a hash prefix: PRIMARY KEY (Digest::NumericHash(id), id) for id Uint64. Signature: Digest::NumericHash(Uint64{Flags:AutoMap}) -> Uint64 (https://ydb.tech/docs/en/yql/reference/udf/list/digest).
• YDB has no SERIAL / AUTO_INCREMENT / CREATE SEQUENCE. Don't emit those keywords in YQL — they'll fail. Use client-generated UUIDs or a hash-prefix + id-service design.
• Partitioning is automatic, defaults need tuning for write-heavy tables. CREATE TABLE … WITH (…) options: AUTO_PARTITIONING_BY_LOAD, AUTO_PARTITIONING_BY_SIZE, AUTO_PARTITIONING_MIN_PARTITIONS_COUNT, AUTO_PARTITIONING_MAX_PARTITIONS_COUNT, AUTO_PARTITIONING_PARTITION_SIZE_MB. Min count should be ≥ node count for write-heavy workloads.
• Secondary indexes need the VIEW IndexName clause to be used on read. Create: ALTER TABLE t ADD INDEX idx_foo GLOBAL ON (foo). Read: SELECT … FROM t VIEW idx_foo WHERE foo = … (https://ydb.tech/docs/en/yql/reference/syntax/select/secondary_index).
• YDB is NOT PostgreSQL. JOIN semantics, DML behavior, transaction isolation, and built-in function names diverge in non-obvious places. Never extrapolate.

Authoritative: https://ydb.tech/docs/en/yql/reference/syntax/create_table and https://ydb.tech/docs/en/concepts/datamodel/table.

Content rules

Route to a specialist skill (ydb-table / ydb-topics / ydb-coordination) when the question is clearly surface-specific. State uncertainty when this file doesn't cover the question — link the relevant doc page instead of improvising.