SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51bceabb2d1b77e6ed80bd857b435118d884507e5b4bdeb5ba7cdd72dc2380e3' 
  AND token = 'WOQrG5P3lsx8lZLmgCp8pvQ+mAGkxEzymBl3yihWzJM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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