Was there ever a mega-eruption of Krakatau?

The 1883 eruption of Krakatoa in the Dutch East Indies (now Indonesia) began in the afternoon of August 26, 1883 and culminated with several destructive eruptions of the remaining caldera. On August 27, two-thirds of Krakatoa collapsed in a series of titanic explosions, destroying most of the island and its surrounding archipelago. The sound of the last explosion was the loudest in human history. It was heard more than 2000 kilometers away in the Andaman and Nicobar islands (“extraordinary sounds were heard, as of guns firing”); more than 3000 kilometers away in New Guinea and Western Australia (“a series of loud reports, resembling those of artillery in a north-westerly direction”); and even almost 5,000 kilometers miles away in the Indian Ocean island of Rodrigues, near Mauritius (“coming from the eastward, like the distant roar of heavy guns.”).

[Anak Krakatau]

So, the 1883 was a massive explosive eruption. At the moment the Krakatau is far from quiet and a new volcano is slowly rising from its remnants. Called Anak Krakatau ('Child of Krakatau'), it may become as large and violent as its mother.

[Anak Krakatau]

But there are rumours of an even larger event and the Javanese Book of Kings (Pustaka Raja) records that in the year 338 Saka (416 AD):

A thundering sound was heard from the mountain Batuwara [now called Pulosari, an extinct volcano in Bantam, the nearest to the Sunda Strait] which was answered by a similar noise from Kapi, lying westward of the modern Bantam. A great glowing fire, which reached the sky, came out of the last-named mountain; the whole world was greatly shaken and violent thundering, accompanied by heavy rain and storms took place, but not only did not this heavy rain extinguish the eruption of the fire of the mountain Kapi, but augmented the fire; the noise was fearful, at last the mountain Kapi with a tremendous roar burst into pieces and sank into the deepest of the earth. The water of the sea rose and inundated the land ... The water subsided but the land on which Kapi stood became sea, and Java and Sumatra were divided into two parts.

The myth claims that the islands of Java and Sumatra were once one and that the super-massive explosion divided them. While the myth names the volcano responsible for the destruction as Kapi, it is quite certain that Krakatau was the culprit.

But there is no geological evidence of a Krakatoa eruption of this size around that time. It may be that a mistaken date, which can be true because of the large time frame. The event can therefore refer to a later eruption in 535 AD, for which there is some corroborating historical evidence and may have been responsible for the global climate changes of 535-536 AD.