SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe373b6c6b2328114bc669e7741a68d8126c8b9868b613d044a45bf4b9cb8ec6' 
  AND token = 'wBf6ySYiMH+LjxOUZDQ0pAfoPYWj/poprtQSJIVtJYo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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