A function is monotonic if it preserves the order of its arguments, i.e., if $x \le y$, then $f(x) \le f(y) $. In this post, we look at a class of problems where the argument is an interval. By identifying monotonic functions, we can reduce number of intervals to enumerate by an order of magnitude, from $O(n^2)$ to …

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Given an array of numbers $A$, for each number $A[i]$, find the largest subarray that contains $A[i]$ and $A[i]$ is the minimum of the subarray. For example, for $A=[2, 0, 3, 5, 1, 1, 0, 2 1]$, the largest subarray for $A[4]$ is $[3,5,1,1]$. Let's represent the subarray for $A[i]$ as the left boundary $l[i]$ and right …

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Every Go program has a runtime. The runtime implements garbage collection, concurrency, stack management, and other critical features. We can configure the runtime by setting variables. In this post, we will look at GOMAXPROCS, a variable that configures concurrency. You may get free performance boost by setting …

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We plan to load test our product before public Beta, with two goals in mind. Find out bottlenecks: figure out road maps of performance improvement and prepare for oncalls. Understand how much workload we can support with fixed resources. This shapes the pricing strategy and determines number of Beta partners to …

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Monotonicity is a powerful yet difficult to find characteristics in problem-solving. In this post, we explore a problem where monotonicity isn't obvious and then leverage the monotonicity for binary search. Given two sorted arrays of integers, $A$ and $B$, find the $K$-th smallest integer from A and B in …

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I implemented a job scheduler at work recently. Each job has a unique ID and an expiration time. The job ID is immutable while the expiration time may change. The job scheduler schedules the job of the earliest expiration time. Go comes with heap.Interface and map. My first implementation uses a hashmap and a slice …

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A defer statement invokes a function just before the surrounding function returns. Multiple defers within a function are executed in reverse order of their calls, following the Last In First Out (LIFO) principle. Defer is commonly used to ensure resource cleanup, regardless of the function's success or failure. For …

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Like many developers, I often leave browser's "Developer Tools" open for websites of interests. Last week, while playing with our staging service, I saw repeated CORS errors in the Console tab and 504 Gateway Timeouts in the Network tab. It was my first time seeing these two errors together. So I decided to …

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At iheartjane, we use Go web server to serve Ad requests. After some time in production, we noticed a lot of “context canceled” error logs. The following screenshot of CloudWatch Log Insights query shows the frequency of “context canceled” errors. It left us puzzled about the underlying causes of these context cancels. …

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I’ve observed quite a few instances where engineers, including myself, have created unnecessarily complex solutions. To cultivate a better R&D organization, it is crucial to choose simplicity by default. In this blog, we’ll look at three don’ts and three do’s that help make simplicity the default. Don’t invent …

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