Dr. Jelle Hellings baking oliebollen, a Dutch pastry typically enjoyed during New Years Eve
Dr. Jelle Hellings baking oliebollen, a Dutch pastry typically enjoyed during New Years Eve

Postdoc Spotlight: Jelle Hellings

Dr. Jelle Hellings is a third-year postdoc working in the Exploratory Systems Lab of Prof. Sadoghi, Department of Computer Science. In this spotlight, he shares a bit about his research, background, future plans, and personal life.

Area of Research
My research is centered around the foundations of data management, with a specific interest in the underlying theory and implementation of high-performance large-scale data management systems. My research has a strong theoretical and algorithmic focus, e.g., the study of lower-bounds on the complexity of problems, finding efficient methods to solve problems that deal with large-scale data sets, and so on.

Currently, I work on the theory and techniques underlying resilient large-scale data management systems that can deal with failures (e.g., due to hardware crashes, software bugs, or malicious behavior). Previously, I worked on various aspects of querying graph data, temporal data, and other forms of unstructured data.

Professional Journey
My journey toward computer science had many detours. When I finished high school in the Netherlands, I had little interest left in further studies and ended up with a gap year working at a cable company. After that, I majored in physics and mathematics, only to find out that that choice did not fit. Hence, I followed a reorientation program and ended up choosing for computer science at the Eindhoven University of Technology, still in the Netherlands.

The switch to computer science turned out to be a great choice: I finished my bachelor and master in five years. Furthermore, my master project-during which I developed methods to construct index structures for very large tree data sets-turned into my first publication at a top venue. As I enjoyed the research for my master project, I decided to continue in research. While looking for places to do so, I got in touch with a database theory research group in Hasselt, Belgium. After finishing my master, I moved to Belgium and started my PhD research as an assistant, a position that involves a high teaching load of around 6 courses per year. My work there primarily focused on the theoretical foundations of data management with a particular focus on graph data and other forms of unstructured data.

In the last stages of my PhD research, I started looking around for new challenges and directions. At that point, I came in contact with prof. Sadoghi at UC Davis, whom was steering his own research into the direction of resilient data management. This new adventure turned out to be a successful endeavor that already resulted in several research publications and a recently-published textbook.

Future Plans
I plan to stay in academics as I love both teaching and research. As such, I am currently in the middle of some serious job searching for a good tenure-track position. Research-wise, there are plenty of open problems in resilient data management to work on in the short term. In the long term, I plan to further delve into the complexities of large-scale processing of graph data, while keeping my eyes open for new directions in data management.

Personal Life
Since 2018, I have been living in Davis-a rather calm life. When I am not working, you can often find me in my kitchen, as I love baking and cooking. Been doing good on that front, as friends and colleagues seem to enjoy my pies and other concoctions. Especially my Kruimelvlaai (a pudding-filled pie with crumb topping from the Netherlands), Dutch apple pie, quiches, and pizzas seem to leave an impression. I will include my Kruimelvlaai recipe below (feel free to contact me for the other recipes).

Besides my work in the kitchen, I also enjoy hanging out with friends (even though that is a bit harder right now), taking walks with friends, bike around, and watching films. I also used to attend the various public events that were typically going on and frequently visited the farmers market for fresh vegetables. Finally, I sometimes play videogames such as StarCraft II.

Kruimelvlaai Recipe

Mix two eggs, 100 g sugar, vanilla extract, and 50 mL milk. Add 70 g all-purpose flour and mix. Bring 500 mL milk to a boil. When boiling, add the egg-mixture. Mix well and keep stirring. Let the pudding simmer for 5 min while stirring. Rapidly cool the pudding, e.g., by putting the pudding in a cold-water bath. Keep stirring initially while cooling to prevent burning at the bottom of the pot. Cover the pot and store in the fridge when done.

Pie crust dough
Mix 200 g all-purpose flour, 100 g dark brown sugar, 80 g butter, some baking powder, ground cinnamon, and salt together. When properly mixed, add 50 mL milk and mix and knead the result together until you have a single solid mass. If the dough is too sticky, add some flour. If the dough is too dry, add some milk. Keep the dough and ingredients cool to ease working with it. When done, cover the dough and store in the fridge.

Do not kneed! Mix 130 g granulated sugar together with vanilla extract. Next, cut 125 g butter into very small pieces and mix together with the sugar. Finally, add 150 g all-purpose flour and mix together with forks until you have a crumble/sand-like result. Do not overwork the mixture (we do not want a dough). Cool the product shortly (e.g., in a freezer) if parts become too sticky.

Assembling the pie
I use a 28 cm springform baking pan. In these forms, it is usually easier to do the bottom and sides separately and I use around 40% of the crust dough for the sides and the rest for the bottom. In traditional pie pans, you can also roll out the crust dough in one piece and fill the pan. Grease the baking pan with some oil and flour to prevent sticking.

After placing the crust, fill the crust with the pudding (should be cool and sturdy by now). Use a spoon to gently distribute the pudding evenly. Add the layer of crumbs (for best results: try to distribute evenly without rearranging). If the sides are too high, then gently push them downward. Bake the pie in a pre-heated oven, 350 °F for 40 min (baking times vary based on oven, hence, check!). For optimal taste, the pie really needs to cool down and settle. Hence, cool the pie down for at-least 8 h (e..g, in the fridge).