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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe9e1339a7daed06e91254b3dcb32384184b1ecf68a273874e0aaa22ea01ff7c' 
  AND token = 'QBYLGhqmU5c19sHdL/ALdB1Aoz2H3cQ+yrZZf6ujeiE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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