SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b861bd2c75de371f9615447e8b556901a35d274bd7ed0553328ad9de02404074' 
  AND token = 'D1GQQyVQRe8WlqhacUrvaUvbRLksBpjaTnWpEu6WvBk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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