SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f280171d16b561c601ad7b9a89141a214520851758768ebba1c536028cbf5ae' 
  AND token = 'NUZTSk4U7x4DlXRZrUbXyNWXtqdVLHIWgIhycTLQ7qA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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