SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81550dc4cd951d3784c608d27fd82995277ab7c57398ddce563701a487fe85a2' 
  AND token = 'ZqlkURmrSjZYZjbwCgntIp8GNVpeIuw639P8tCJPeUg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00013

JSON explain

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