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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'be2a9069ce4ee4285909a67664c7767928ef5c8e251364fb10dd94f450f6f9f9' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}