SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7892724b790547dd6f95e291d537f2d7f25cb78a80c536ccf8b6843d75e9dc23' 
  AND token = 'adG4btjzyGxBOHu+ZYar4YIvHDx3/Yb5gFBZQFeVdSs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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