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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cbaf31d2ab39ef70680adb8ff264bd69a4a2e72b8c46b61d3eed018c15f76bc4' 
  AND token = 'qE2eUgWt+jiL62Ev8HKAmI4SCUXNz9Ul0ykL0PtSDsE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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