SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '862c6829435bda440ef41b4e29e8dd2ec308b62a411234694b3f33bd2b699615' 
  AND token = 'NnzQf3KexRFjKCOwfy+BOTdvaS97MMuDEkNONzVur6Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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