SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5c0b6090e76f121ae1b41c5217fe3605427325b6208af09054c808294e7f4950' 
  AND token = 'k8cvfnIYE7FOmwUrF00OvixlZtIiTXeZksPFnMCeExA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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