SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '908c0887489006146ebba135ed7f562e477686dddf05272c6ab453c2f86156a3' 
  AND token = 'SKY5QyiWT+ZkuIhvQtgsigiENCJM0zf4HTVYccVzMkc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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