"Babylon Revisited," as we discuss in "In a Nutshell," is largely considered to be the greatest of Fitzgerald's short stories. Its literary merit is indisputable; you'll find us gushing over the brilliant bits in "Quotes." This story is a masterpiece whose focus is character and theme, not so much plot or meeting the expectations of genre fiction. So we're going to consider "Babylon Revisited" as literary fiction.
Our classification of roman à clef is slightly a misnomer, since this French phrase literally means "novel with a key," and "Babylon Revisited" is obviously a short story. Perhaps nouvelle à clef would be better. The point is that "Babylon Revisited" is sufficiently rooted in Fitzgerald's own personal experiences that we can consider it a thinly veiled, largely artistic rendering of a period in his own life. Of course, Fitzgerald takes great artistic license in crafting this story, and it is at the end of the day fiction. But it doesn't mean we can't take great interest in examining the connections between Charlie Wales and F. Scott himself.
Starting with the general stuff, we know that the Fitzgeralds were in and out of Paris a lot in the 1920s, and lived there on and off. Fitzgerald used to hang out at the Ritz bar with guys like Ernest Hemingway; the Ritz bar was an American hangout for the expatriates in Paris. Fitzgerald had a daughter named Scottie who was nine years old when he wrote "Babylon Revisited" (Honoria is nine in the text). In a letter to his daughter, Fitzgerald explicitly states that she was the basis for the character of Honoria Wales: "I sold 'Babylon Revisited,' in which you are a character" he told her (source: The Letters of F. Scott Fitzgerald, edited by Andrew Turnbull, published by Bodey Head, 1964).
There are even specific events in "Babylon Revisited" that are taken straight from Fitzgerald's life: Lorraine's reminiscence about the stolen tricycle is one example. Fitzgerald, in 1929, indeed stole a baker's tricycle and pedaled all over Paris with it, "thumping the Russian doormen with a long loaf of bread" (Source: James R. Mellow, Invented Lives: F. Scott and Zelda Fitzgerald. Boston: Houghton Mifflin Co., 1984).
Of course, anyone who's heard about F. Scott Fitzgerald probably knows that he was big on the drinking and extravagance, and that his marriage to Zelda Fitzgerald was full of intense drama. It was all documented in letters back and forth between the spouses. Charlie's comment that he and Helen "had senselessly begun to abuse each other's love, tear it into shreds" is likely rooted in his own tumultuous marriage to Zelda. If the rocky marriage interests you, we suggest reading The Beautiful and Damned, which is another artistic rendering of the couple's tragic relationship. Zelda ended up in a sanitarium for schizophrenia in 1930, and her poor health was likely aggravated by F. Scott's constant drinking. As she wrote in a letter to her husband: "You were literally eternally drunk" (source: Sally Cline, Zelda Fitzgerald).
Charlie's antagonistic relationship with Marion parallels Fitzgerald's own hostile interactions with Zelda's sister, Rosalind Sayre (as detailed in James R. Mellow's Inverted Lives: F. Scott and Zelda Fitzgerald). When Zelda was taken to a sanitarium, Rosalind wanted to take custody of Scottie because she felt F. Scott was an alcoholic and not fit to be a father. There's a plethora of angry letters back and forth between the two of them.
Lastly, we can interpret "Babylon Revisited" as historical fiction because it is rooted in the historical events of the 1920s and 30s. We give a primer on the history and discuss its relevance to the story in detail in "Setting," so check it out if you're interested.