SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9fc81f3850b334b0af93596eab919f9427e553517dc1c24bdd555360550362da' 
  AND token = 'SdWRlvvCjvRz2dJvGHf2sIZzoJxi47rIZDfXM75bVhs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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