> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pg-sharding.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Default shard

A distribution can have a default shard that acts as a catch-all fallback. When the router matches a query to a distribution with a default shard, it is guaranteed to find a route — even if the sharding key doesn't fall within any explicitly defined key range.

The default shard is implemented as a special key range with the minimum possible value as its lower bound. This key range has a reserved ID: `{DistributionId}.DEFAULT`.

For example, if the distribution has column types `[varchar, integer, uuid]`, the default key range lower bound is `["", -9223372036854775808, "00000000-0000-0000-0000-000000000000"]`.

```sql theme={null}
-- Setup: key ranges kr1: [-20, -10) → sh2, kr2: [-10, 0) → sh3, kr3: [0, ∞) → sh4
-- Default shard: sh1 (covers MinInt64 to -20)

INSERT INTO t(id) VALUES (-30);  -- → sh1 (default, below all explicit ranges)
INSERT INTO t(id) VALUES (-20);  -- → sh2 (kr1)
INSERT INTO t(id) VALUES (-10);  -- → sh3 (kr2)
INSERT INTO t(id) VALUES (0);    -- → sh4 (kr3)
```

See [Default Shard](/sharding/default_shard) for more details.