private static String createCacheFileName(ConfigCacheKey key) {
        final ConfigKey<?> configKey = key.getKey();
        return configKey.getNamespace() + "." + configKey.getName() + separator + configKey.getConfigId().replaceAll("/", "_") +
                separator + key.getDefMd5();
    }
Put in cache, except when config has an error

@param config config to update in cache
config-proxy/src/main/java/com/yahoo/vespa/config/proxy/MemoryCache.java