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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b5bff8fc2d8cd82eee1f3fc439d8bdaab6bbbf8004665ab49233e70b18a83db' 
  AND token = 'cDKgneG/u9SoCwWg2Xls7kXbsrbpLaip5FllKIkeISc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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