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Last Value Cache (LVC)

The Last Value Cache maintains the most recent row per key in a small table, updated by a trigger on every write. Status widgets, current-value tiles, and real-time alerts read from that table instead of scanning a ChronoTable for MAX(time) on each refresh, which keeps lookups in the sub-10ms range.

Enable LVC​

SELECT lakets.enable_lvc(
    'system_metrics',
    key_columns   := ARRAY['host'],
    value_columns := ARRAY['cpu', 'memory']
);

This creates _lvc_system_metrics and an AFTER INSERT trigger that upserts into the cache table on every write to system_metrics.

Query the cache​

INSERT INTO system_metrics
VALUES (now(), 'web-01', 'us-west-2', 'prod', 85.0, 7000, 500);

-- The cache reflects this immediately
SELECT * FROM _lvc_system_metrics;
-- host   | cpu  | memory | last_updated
-- web-01 | 85.0 | 7000   | 2026-03-25 17:30:01

Cache statistics​

SELECT * FROM lakets.lvc_stats();

Returns hit count, miss count, last_updated_at per LVC-enabled ChronoTable.

When to use​

Use caseLVC vs raw query
Status widget showing "current CPU per host"LVC — millisecond reads
Real-time alert checking last valueLVC
Historical aggregations (averages, percentiles)Raw ChronoTable or RollUp
Time-window queries (last 1h, last 30d)Raw ChronoTable or RollUp