---
type: Reference
title: ScalarDB Configurations
description: This page describes the available configurations for ScalarDB.
resource: https://scalardb-community.scalar-labs.com/docs/latest/configurations/
tags:
- scalardb-community
- v3.13
- phase:implement
status: stable
product: scalardb-community
product_title: ScalarDB Community
version: '3.13'
doc_id: configurations
lifecycle_phase: implement
generated:
  by: process:okf-build/1.0.0
  at: '2026-08-10T20:40:05Z'
sources:
- id: docs-scalardb-community
  resource: https://github.com/scalar-labs/docs-scalardb-community/blob/71d199cb0df1c638bd7e305b64fa09fc7236e5c4/docs/configurations.mdx
  title: ScalarDB Community documentation source (MDX)
  author: process:scalar-labs/docs-scalardb-community
  last_modified: '2025-04-07T11:32:02Z'
---

# ScalarDB Configurations

This page describes the available configurations for ScalarDB.

## ScalarDB client configurations

This section describes the configurations for the ScalarDB client. ScalarDB provides ways to run transactions by using Consensus Commit, run non-transactional storage operations, and run transactions through ScalarDB Cluster.

### Run transactions by using Consensus Commit

ScalarDB provides its own transaction protocol called Consensus Commit, which is the default transaction manager type in ScalarDB. To use the Consensus Commit transaction manager, add the following to the ScalarDB properties file:

```properties
scalar.db.transaction_manager=consensus-commit
```

:::note

If you don't specify the `scalar.db.transaction_manager` property, `consensus-commit` will be the default value.

:::

#### Basic configurations

The following basic configurations are available for the Consensus Commit transaction manager:

| Name                                                  | Description                                                                                                                                                                                                                                                                                                                                                                                                  | Default       |
|-------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|
| `scalar.db.transaction_manager`                       | `consensus-commit` should be specified.                                                                                                                                                                                                                                                                                                                                                                      | -             |
| `scalar.db.consensus_commit.isolation_level`          | Isolation level used for Consensus Commit. Either `SNAPSHOT` or `SERIALIZABLE` can be specified.                                                                                                                                                                                                                                                                                                             | `SNAPSHOT`    |
| `scalar.db.consensus_commit.serializable_strategy`    | Serializable strategy used for Consensus Commit. Either `EXTRA_READ` or `EXTRA_WRITE` can be specified. If `SNAPSHOT` is specified in the property `scalar.db.consensus_commit.isolation_level`, this configuration will be ignored.                                                                                                                                                                         | `EXTRA_READ`  |
| `scalar.db.consensus_commit.coordinator.namespace`    | Namespace name of Coordinator tables.                                                                                                                                                                                                                                                                                                                                                                        | `coordinator` |
| `scalar.db.consensus_commit.include_metadata.enabled` | If set to `true`, `Get` and `Scan` operations results will contain transaction metadata. To see the transaction metadata columns details for a given table, you can use the `DistributedTransactionAdmin.getTableMetadata()` method, which will return the table metadata augmented with the transaction metadata columns. Using this configuration can be useful to investigate transaction-related issues. | `false`       |

#### Performance-related configurations

The following performance-related configurations are available for the Consensus Commit transaction manager:

| Name                                                                                   | Description                                                                                                                                                                                                                                                                               | Default                                                           |
|----------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------|
| `scalar.db.consensus_commit.parallel_executor_count`                                   | Number of executors (threads) for parallel execution.                                                                                                                                                                                                                                     | `128`                                                             |
| `scalar.db.consensus_commit.parallel_preparation.enabled`                              | Whether or not the preparation phase is executed in parallel.                                                                                                                                                                                                                             | `true`                                                            |
| `scalar.db.consensus_commit.parallel_validation.enabled`                               | Whether or not the validation phase (in `EXTRA_READ`) is executed in parallel.                                                                                                                                                                                                            | The value of `scalar.db.consensus_commit.parallel_commit.enabled` |
| `scalar.db.consensus_commit.parallel_commit.enabled`                                   | Whether or not the commit phase is executed in parallel.                                                                                                                                                                                                                                  | `true`                                                            |
| `scalar.db.consensus_commit.parallel_rollback.enabled`                                 | Whether or not the rollback phase is executed in parallel.                                                                                                                                                                                                                                | The value of `scalar.db.consensus_commit.parallel_commit.enabled` |
| `scalar.db.consensus_commit.async_commit.enabled`                                      | Whether or not the commit phase is executed asynchronously.                                                                                                                                                                                                                               | `false`                                                           |
| `scalar.db.consensus_commit.async_rollback.enabled`                                    | Whether or not the rollback phase is executed asynchronously.                                                                                                                                                                                                                             | The value of `scalar.db.consensus_commit.async_commit.enabled`    |
| `scalar.db.consensus_commit.parallel_implicit_pre_read.enabled`                        | Whether or not implicit pre-read is executed in parallel.                                                                                                                                                                                                                                 | `true`                                                            |
| `scalar.db.consensus_commit.coordinator.group_commit.enabled`                          | Whether or not committing the transaction state is executed in batch mode. This feature can't be used with a two-phase commit interface.                                                                                                                                                  | `false`                                                           |
| `scalar.db.consensus_commit.coordinator.group_commit.slot_capacity`                    | Maximum number of slots in a group for the group commit feature. A large value improves the efficiency of group commit, but may also increase latency and the likelihood of transaction conflicts.[^1]                                                                                    | `20`                                                              |
| `scalar.db.consensus_commit.coordinator.group_commit.group_size_fix_timeout_millis`    | Timeout to fix the size of slots in a group. A large value improves the efficiency of group commit, but may also increase latency and the likelihood of transaction conflicts.[^1]                                                                                                        | `40`                                                              |
| `scalar.db.consensus_commit.coordinator.group_commit.delayed_slot_move_timeout_millis` | Timeout to move delayed slots from a group to another isolated group to prevent the original group from being affected by delayed transactions. A large value improves the efficiency of group commit, but may also increase the latency and the likelihood of transaction conflicts.[^1] | `1200`                                                            |
| `scalar.db.consensus_commit.coordinator.group_commit.old_group_abort_timeout_millis`   | Timeout to abort an old ongoing group. A small value reduces resource consumption through aggressive aborts, but may also increase the likelihood of unnecessary aborts for long-running transactions.                                                                                    | `60000`                                                           |
| `scalar.db.consensus_commit.coordinator.group_commit.timeout_check_interval_millis`    | Interval for checking the group commit–related timeouts.                                                                                                                                                                                                                                  | `20`                                                              |
| `scalar.db.consensus_commit.coordinator.group_commit.metrics_monitor_log_enabled`      | Whether or not the metrics of the group commit are logged periodically.                                                                                                                                                                                                                   | `false`                                                           |

#### Underlying storage or database configurations

Consensus Commit has a storage abstraction layer and supports multiple underlying storages. You can specify the storage implementation by using the `scalar.db.storage` property.

Select a database to see the configurations available for each storage.

**JDBC databases**

The following configurations are available for JDBC databases:

| Name                                                      | Description                                                                                                                                                                  | Default                      |
|-----------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------|
| `scalar.db.storage`                                       | `jdbc` must be specified.                                                                                                                                                    | -                            |
| `scalar.db.contact_points`                                | JDBC connection URL.                                                                                                                                                         |                              |
| `scalar.db.username`                                      | Username to access the database.                                                                                                                                             |                              |
| `scalar.db.password`                                      | Password to access the database.                                                                                                                                             |                              |
| `scalar.db.jdbc.connection_pool.min_idle`                 | Minimum number of idle connections in the connection pool.                                                                                                                   | `20`                         |
| `scalar.db.jdbc.connection_pool.max_idle`                 | Maximum number of connections that can remain idle in the connection pool.                                                                                                   | `50`                         |
| `scalar.db.jdbc.connection_pool.max_total`                | Maximum total number of idle and borrowed connections that can be active at the same time for the connection pool. Use a negative value for no limit.                        | `100`                        |
| `scalar.db.jdbc.prepared_statements_pool.enabled`         | Setting this property to `true` enables prepared-statement pooling.                                                                                                          | `false`                      |
| `scalar.db.jdbc.prepared_statements_pool.max_open`        | Maximum number of open statements that can be allocated from the statement pool at the same time. Use a negative value for no limit.                                         | `-1`                         |
| `scalar.db.jdbc.isolation_level`                          | Isolation level for JDBC. `READ_UNCOMMITTED`, `READ_COMMITTED`, `REPEATABLE_READ`, or `SERIALIZABLE` can be specified.                                                       | Underlying-database specific |
| `scalar.db.jdbc.table_metadata.schema`                    | Schema name for the table metadata used for ScalarDB.                                                                                                                        | `scalardb`                   |
| `scalar.db.jdbc.table_metadata.connection_pool.min_idle`  | Minimum number of idle connections in the connection pool for the table metadata.                                                                                            | `5`                          |
| `scalar.db.jdbc.table_metadata.connection_pool.max_idle`  | Maximum number of connections that can remain idle in the connection pool for the table metadata.                                                                            | `10`                         |
| `scalar.db.jdbc.table_metadata.connection_pool.max_total` | Maximum total number of idle and borrowed connections that can be active at the same time for the connection pool for the table metadata. Use a negative value for no limit. | `25`                         |
| `scalar.db.jdbc.admin.connection_pool.min_idle`           | Minimum number of idle connections in the connection pool for admin.                                                                                                         | `5`                          |
| `scalar.db.jdbc.admin.connection_pool.max_idle`           | Maximum number of connections that can remain idle in the connection pool for admin.                                                                                         | `10`                         |
| `scalar.db.jdbc.admin.connection_pool.max_total`          | Maximum total number of idle and borrowed connections that can be active at the same time for the connection pool for admin. Use a negative value for no limit.              | `25`                         |

:::note

If you use SQLite3 as a JDBC database, you must set `scalar.db.contact_points` as follows.

```properties
scalar.db.contact_points=jdbc:sqlite:<YOUR_DB>.sqlite3?busy_timeout=10000
```

Unlike other JDBC databases, [SQLite3 does not fully support concurrent access](https://www.sqlite.org/lang_transaction.html).
To avoid frequent errors caused internally by [`SQLITE_BUSY`](https://www.sqlite.org/rescode.html#busy), we recommend setting a [`busy_timeout`](https://www.sqlite.org/c3ref/busy_timeout.html) parameter.

:::

**DynamoDB**

The following configurations are available for DynamoDB:

| Name                                        | Description                                                                                                                                                                                                                                                 | Default    |
|---------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------|
| `scalar.db.storage`                         | `dynamo` must be specified.                                                                                                                                                                                                                                 | -          |
| `scalar.db.contact_points`                  | AWS region with which ScalarDB should communicate (e.g., `us-east-1`).                                                                                                                                                                                      |            |
| `scalar.db.username`                        | AWS access key used to identify the user interacting with AWS.                                                                                                                                                                                              |            |
| `scalar.db.password`                        | AWS secret access key used to authenticate the user interacting with AWS.                                                                                                                                                                                   |            |
| `scalar.db.dynamo.endpoint_override`        | Amazon DynamoDB endpoint with which ScalarDB should communicate. This is primarily used for testing with a local instance instead of an AWS service.                                                                                                        |            |
| `scalar.db.dynamo.table_metadata.namespace` | Namespace name for the table metadata used for ScalarDB.                                                                                                                                                                                                    | `scalardb` |
| `scalar.db.dynamo.namespace.prefix`         | Prefix for the user namespaces and metadata namespace names. Since AWS requires having unique tables names in a single AWS region, this is useful if you want to use multiple ScalarDB environments (development, production, etc.) in a single AWS region. |            |

**Cosmos DB for NoSQL**

The following configurations are available for CosmosDB for NoSQL:

| Name                                       | Description                                                                                              | Default    |
|--------------------------------------------|----------------------------------------------------------------------------------------------------------|------------|
| `scalar.db.storage`                        | `cosmos` must be specified.                                                                              | -          |
| `scalar.db.contact_points`                 | Azure Cosmos DB for NoSQL endpoint with which ScalarDB should communicate.                               |            |
| `scalar.db.password`                       | Either a master or read-only key used to perform authentication for accessing Azure Cosmos DB for NoSQL. |            |
| `scalar.db.cosmos.table_metadata.database` | Database name for the table metadata used for ScalarDB.                                                  | `scalardb` |
| `scalar.db.cosmos.consistency_level`       | Consistency level used for Cosmos DB operations. `STRONG` or `BOUNDED_STALENESS` can be specified.       | `STRONG`   |

**Cassandra**

The following configurations are available for Cassandra:

| Name                                    | Description                                                           | Default    |
|-----------------------------------------|-----------------------------------------------------------------------|------------|
| `scalar.db.storage`                     | `cassandra` must be specified.                                        | -          |
| `scalar.db.contact_points`              | Comma-separated contact points.                                       |            |
| `scalar.db.contact_port`                | Port number for all the contact points.                               |            |
| `scalar.db.username`                    | Username to access the database.                                      |            |
| `scalar.db.password`                    | Password to access the database.                                      |            |
| `scalar.db.cassandra.metadata.keyspace` | Keyspace name for the namespace and table metadata used for ScalarDB. | `scalardb` |

##### Multi-storage support

ScalarDB supports using multiple storage implementations simultaneously. You can use multiple storages by specifying `multi-storage` as the value for the `scalar.db.storage` property.

For details about using multiple storages, see [Multi-Storage Transactions](./multi-storage-transactions.md).

##### Cross-partition scan configurations

By enabling the cross-partition scan option as described below, the `Scan` operation can retrieve all records across partitions. In addition, you can specify arbitrary conditions and orderings in the cross-partition `Scan` operation by enabling `cross_partition_scan.filtering` and `cross_partition_scan.ordering`, respectively. Currently, the cross-partition scan with ordering option is available only for JDBC databases. To enable filtering and ordering, `scalar.db.cross_partition_scan.enabled` must be set to `true`.

For details on how to use cross-partition scan, see [Scan operation](./api-guide.md#scan-operation).

:::warning

For non-JDBC databases, transactions could be executed at read-committed snapshot isolation (`SNAPSHOT`), which is a lower isolation level, even if you enable cross-partition scan with the `SERIALIZABLE` isolation level. When using non-JDBC databases, use cross-partition scan only if consistency does not matter for your transactions.

:::

| Name                                               | Description                                   | Default |
|----------------------------------------------------|-----------------------------------------------|---------|
| `scalar.db.cross_partition_scan.enabled`           | Enable cross-partition scan.                  | `true`  |
| `scalar.db.cross_partition_scan.filtering.enabled` | Enable filtering in cross-partition scan.     | `false` |
| `scalar.db.cross_partition_scan.ordering.enabled`  | Enable ordering in cross-partition scan.      | `false` |

### Run non-transactional storage operations

To run non-transactional storage operations, you need to configure the `scalar.db.transaction_manager` property to `single-crud-operation`:

```properties
scalar.db.transaction_manager=single-crud-operation
```

Also, you need to configure the underlying storage or database as described in [Underlying storage or database configurations](#underlying-storage-or-database-configurations).

### Run transactions through ScalarDB Cluster

[ScalarDB Cluster (redirects to the Enterprise docs site)](https://scalardb.scalar-labs.com/docs/latest/scalardb-cluster/) is a component that provides a gRPC interface to ScalarDB.

For details about client configurations, see the ScalarDB Cluster [client configurations (redirects to the Enterprise docs site)](https://scalardb.scalar-labs.com/docs/latest/scalardb-cluster/developer-guide-for-scalardb-cluster-with-java-api/#client-configurations).

## Other ScalarDB configurations

The following are additional configurations available for ScalarDB:

| Name                                                             | Description                                                                                                                                                                                 | Default              |
|------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------|
| `scalar.db.metadata.cache_expiration_time_secs`                  | ScalarDB has a metadata cache to reduce the number of requests to the database. This setting specifies the expiration time of the cache in seconds.                                         | `-1` (no expiration) |
| `scalar.db.active_transaction_management.expiration_time_millis` | ScalarDB maintains ongoing transactions, which can be resumed by using a transaction ID. This setting specifies the expiration time of this transaction management feature in milliseconds. | `-1` (no expiration) |
| `scalar.db.default_namespace_name`                               | The given namespace name will be used by operations that do not already specify a namespace.                                                                                                |                      |

## Placeholder usage

You can use placeholders in the values, and they are replaced with environment variables (`${env:<ENVIRONMENT_VARIABLE_NAME>}`) or system properties (`${sys:<SYSTEM_PROPERTY_NAME>}`). You can also specify default values in placeholders like `${sys:<SYSTEM_PROPERTY_NAME>:-<DEFAULT_VALUE>}`.

The following is an example of a configuration that uses placeholders:

```properties
scalar.db.username=${env:<SCALAR_DB_USERNAME>:-admin}
scalar.db.password=${env:<SCALAR_DB_PASSWORD>}
```

In this example configuration, ScalarDB reads the username and password from environment variables. If the environment variable `SCALAR_DB_USERNAME` does not exist, ScalarDB uses the default value `admin`.

## Configuration examples

This section provides some configuration examples.

### Configuration example #1 - App and database

```mermaid
flowchart LR
    app["<b>App</b><br />(ScalarDB library with<br />Consensus Commit)"]
    db[(Underlying storage or database)]
    app --> db
```

In this example configuration, the app (ScalarDB library with Consensus Commit) connects to an underlying storage or database (in this case, Cassandra) directly.

:::warning

This configuration exists only for development purposes and isn’t suitable for a production environment. This is because the app needs to implement the [Scalar Admin](https://github.com/scalar-labs/scalar-admin) interface to take transactionally consistent backups for ScalarDB, which requires additional configurations.

:::

The following is an example of the configuration for connecting the app to the underlying database through ScalarDB:

```properties
# Transaction manager implementation.
scalar.db.transaction_manager=consensus-commit

# Storage implementation.
scalar.db.storage=cassandra

# Comma-separated contact points.
scalar.db.contact_points=<CASSANDRA_HOST>

# Credential information to access the database.
scalar.db.username=<USERNAME>
scalar.db.password=<PASSWORD>
```

### Configuration example #2 - App, ScalarDB Cluster, and database

```mermaid
flowchart LR
    app["App -<br />ScalarDB library with gRPC"]
    cluster["ScalarDB Cluster -<br />(ScalarDB library with<br />Consensus Commit)"]
    db[(Underlying storage or database)]
    app --> cluster --> db
```

In this example configuration, the app (ScalarDB library with gRPC) connects to an underlying storage or database (in this case, Cassandra) through ScalarDB Cluster, which is a component that is available only in the ScalarDB Enterprise edition.

:::note

This configuration is acceptable for production use because ScalarDB Cluster implements the [Scalar Admin](https://github.com/scalar-labs/scalar-admin) interface, which enables you to take transactionally consistent backups for ScalarDB by pausing ScalarDB Cluster.

:::

The following is an example of the configuration for connecting the app to the underlying database through ScalarDB Cluster:

```properties
# Transaction manager implementation.
scalar.db.transaction_manager=cluster

# Contact point of the cluster.
scalar.db.contact_points=indirect:<SCALARDB_CLUSTER_CONTACT_POINT>
```

For details about client configurations, see the ScalarDB Cluster [client configurations (redirects to the Enterprise docs site)](https://scalardb.scalar-labs.com/docs/3.10/scalardb-cluster/developer-guide-for-scalardb-cluster-with-java-api/#client-configurations).

[^1]: It's worth benchmarking the performance with a few variations (for example, 75% and 125% of the default value) on the same underlying storage that your application uses, considering your application's access pattern, to determine the optimal configuration as it really depends on those factors. Also, it's important to benchmark combinations of these parameters (for example, first, `slot_capacity:20` and `group_size_fix_timeout_millis:40`; second, `slot_capacity:30` and `group_size_fix_timeout_millis:40`; and third, `slot_capacity:20` and `group_size_fix_timeout_millis:80`) to determine the optimal combination.
