SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'da521fd9281435cd2eb9fd075238736dc35d8b9d1027f5dae6f6b252cb648b4b' 
  AND token = 'w/RqCz2JrGjTqxGTTQmWCCzBwvywtvZJfZZjqS9bGZQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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