SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fe18614a9160b452f0b17142b2a2d35b25617c3b99ed0803aa93f342f62b195' 
  AND token = 'XzztXBMKGqC866LoVfVm4YRl758cFcZzlS0jPePvuNM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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