SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f849ebecbe45d2c9548845f718c6f80636be1b740853f5b4aea932e2643bddf3' 
  AND token = 'LaCK8zqkfa9fVT5btJj8Hlo05tJhpp4tWmKxHWh3Su4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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