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To ensure consistency, it is important that the PowerSync Service does not interpret the same source row in different ways after updating to a new version. At the same time, we want to fix bugs or other inaccuracies that have accumulated during the development of the Service.

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Overview

To make this trade‑off explicit, you choose whether to keep the existing behavior or turn on newer fixes that slightly change how data is processed. Use the config block in your Sync Rules YAML file to choose the behavior. There are two ways to turn fixes on:
  1. Set an edition to enable the full set of fixes for that edition. This is the recommended approach for new projects.
  2. Toggle individual options for more fine‑grained control.
For older projects, the previous behavior remains the default. New projects should enable all current fixes.

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Configuration

For new projects, it is recommended to enable all current fixes by setting edition: <edition>:
sync_rules.yaml
config:
  edition: 2 # Recommended to set to the latest available edition (see 'Supported fixes' table below)

bucket_definitions:
  # ...
Or, specify options individually:
sync_rules.yaml
config:
  timestamps_iso8601: true
  versioned_bucket_ids: true
  fixed_json_extract: true
  custom_postgres_types: true

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Supported fixes

This table lists all fixes currently supported:
NameExplanationAdded in Service versionFixed in edition
timestamps_iso8601Link1.15.02
versioned_bucket_idsLink1.15.02
fixed_json_extractLink1.15.02
custom_postgres_typesLink.1.15.32

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timestamps_iso8601

PowerSync is supposed to encode timestamps according to the ISO-8601 standard. Without this fix, the service encoded timestamps from MongoDB and Postgres source databases incorrectly. To ensure time values from Postgres compare lexicographically, they’re also padded to six digits of accuracy when encoded. Since MongoDB only stores values with an accuracy of milliseconds, only three digits of accuracy are used. For instance, the value 2025-09-22T14:29:30 would be encoded as follows:
  • For Postgres: 2025-09-22 14:29:30 without the fix, 2025-09-22T14:29:30.000000 with the fix applied.
  • For MongoDB: 2025-09-22 14:29:30.000 without the fix, 2025-09-22T14:29:30.000 with the fix applied.
Note that MySQL has never been affected by this issue, and thus behaves the same regardless of the option used.

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Configurable sub-second datetime precision

When the timestamps_iso8601 option is enabled, PowerSync will synchronize date and time values with a higher precision depending on the source database. You can use the timestamp_max_precision option to configure the actual precision to use. For instance, a Postgres timestamp value would sync as 2025-09-22T14:29:30.000000 by default. If you don’t want that level of precision, you can use the following options to make it sync as 2025-09-22T14:29:30.000:
sync_rules.yaml
config:
  edition: 2
  timestamp_max_precision: milliseconds
Valid options for timestamp_max_precision are seconds, milliseconds, microseconds and nanoseconds. When an explicit value is given, all synced time values will use that precision. If a source value has a higher precision, it will be truncated (it is not rounded). If a source value has a lower precision, it will be padded (so setting the option to microseconds with a MongoDB source database will sync values as 2025-09-22T14:29:30.123000, with the last three sub-second digits always being set to zero). If no option is given, the default precision depends on the source database:
Source databaseDefault precisionMax precisionNotes
MongoDBMillisecondsMilliseconds
PostgresMicrosecondsMicroseconds
MySQLMillisecondsMicrosecondsDefaults to milliseconds, but can be expanded with the option.
SQL ServerNanosecondsNanosecondsSQL Server supports 7 digits of accuracy, the sync service pads values to always use 9 for nanoseconds.

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versioned_bucket_ids

Sync Rules define buckets, which rows to sync are then assigned to. When you run a full defragmentation or redeploy Sync Rules, the same bucket identifiers are re-used when processing data again. Because the second iteration uses different checksums for the same bucket ids, clients may sync data twice before realizing that something is off and starting from scratch. Applying this fix improves client-side progress estimation and is more efficient, since data would not get downloaded twice.

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fixed_json_extract

This fixes the json_extract functions as well as the -> and ->> operators in sync rules to behave similar to recent SQLite versions: We only split on . if the path starts with $.. For instance, 'json_extract({"foo.bar": "baz"}', 'foo.bar') would evaluate to:
  1. baz with the option enabled.
  2. null with the option disabled.

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custom_postgres_types

If you have custom Postgres types in your backend database schema, older versions of the PowerSync Service would not recognize these values and sync them with the textual wire representation used by Postgres. This is especially noticeable when defining DOMAIN types with e.g. a REAL inner type: The wrapped DOMAIN type should get synced as a real value as well, but it would actually get synced as a string. With this fix applied:
  • DOMAIN TYPEs are synced as their inner type.
  • Array types of custom types get parsed correctly, and sync as a JSON array.
  • Custom types get parsed and synced as a JSON object containing their members.
  • Ranges sync as a JSON object corresponding to the following TypeScript definition: 
    export type Range<T> =
  | {
      lower: T | null;
      upper: T | null;
      lower_exclusive: boolean;
      upper_exclusive: boolean;
      }
  | 'empty';
  • Multi-ranges sync as an array of ranges.