SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3408f68c1890b638385e486a747b98c8adce3a8c5de90571dfb875696f023ee2' 
  AND token = 'VzWSEelkZJLq15NQiXuTcJiuoWa4TjRhjmzUzen0UDo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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