SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b81259e06899dc24f92e759b242a140c537a26283f321b1b887be5e5207d289b' 
  AND token = 'xs5LnOog0PZPWWMBpa338kMOZ5rCp9gxrO+2iN1+5lI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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