SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e39bceb7f7c0df77352999280faef55e8d1e3644140594effca721a9e55580ab' 
  AND token = 'VjK+OD92XXor59jQzXKGmXETrm0xLNxzGchVTb9DkR8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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