Backend – What is a backend engineer?
A backend engineer is responsible for the server-side application logic and integration of the work front-end engineers do. Backend engineers are usually write the web services and APIs used by front-end engineers and mobile application engineers. The application logic is calculated using a server-site programming language such as Java, C++, C#, Python, Javascript, etc which backend engineers must have a strong understanding of. They are also responsible for saving, updating, and reading data from the database which means they must have a decent amount of knowledge of databases.
Improve Your Coding Skills
Years of experience do not automatically make you a better programmer. I have met developers with a decade on the job who write the same mediocre code they wrote in year two. The difference between a good developer and a great one is deliberate practice — consistently pushing yourself outside your comfort zone with focused, intentional effort.
Build Real Projects, Not Just Tutorials
Following along with a tutorial gives you the illusion of understanding. Building something from scratch forces you to solve real problems. When you build a side project — a REST API, a personal finance tracker, a CLI tool — you hit walls that tutorials never show you: debugging cryptic errors, designing schemas, handling edge cases. That struggle is where actual learning happens.
Put every project on GitHub. Even if the code is rough, a public portfolio signals that you ship things.
Read Other People’s Code
Most developers only read code when fixing a bug. That is a missed opportunity. Reading well-written open source code is like studying how great authors write. Pick a library you use daily — Spring Boot, Express, Django — and read through its source. You will discover patterns you would never invent on your own.
Start small. Read a single module or utility class. Pay attention to naming, error handling, and organization.
Practice Algorithmic Thinking
Platforms like LeetCode and HackerRank are not just for interview prep. They train you to break complex problems into smaller, solvable pieces. When you practice with hash maps, trees, and graphs, you start recognizing which tool fits which problem.
Aim for two to three problems per week. Focus on understanding the approach rather than memorizing solutions.
Write Tests for Everything
Writing tests forces you to think about your code from the outside in. If your code is hard to test, it is probably poorly designed. Tests expose tight coupling, unclear interfaces, and hidden dependencies. Developers who write tests consistently produce cleaner, more modular code.
Start with unit tests for pure functions, then work up to integration tests. Solid test coverage gives you the confidence to refactor aggressively.
Master Your Tools
Your IDE is the most powerful tool you own — learn to use it fully. Most developers use maybe 20 percent of what IntelliJ, VS Code, or Vim can do. Learn keyboard shortcuts for refactoring, navigation, and debugging. Master the integrated debugger instead of relying on print statements.
Beyond the IDE, learn Git beyond add, commit, and push — understand rebase, cherry-pick, bisect, and stash.
Use Code Reviews as a Learning Tool
Code reviews are not just a quality gate — they are one of the fastest ways to learn from senior developers. When someone suggests a better approach in your PR, do not just accept the change. Understand why it is better. Study the pattern so you can apply it next time.
Equally valuable: review other people’s code. Reading PRs from experienced engineers teaches you how they think about architecture.
Contribute to Open Source
Contributing to open source puts you in a professional-grade development workflow — branching strategies, CI/CD pipelines, code review from strangers who hold a high bar. Start with documentation fixes, small bug patches, or adding test coverage.
Learn Multiple Languages
Learning a second or third language does not just expand your resume — it fundamentally changes how you think about code. A Java developer who learns Python discovers the power of simplicity. A Python developer who learns Go understands explicit error handling and static typing. Each language teaches principles you bring back to your primary stack.
Join Developer Communities
Programming can be isolating, and isolation slows growth. Being part of a community exposes you to problems and solutions you would never encounter alone. Join language-specific groups on Discord, Reddit, or Slack. When you explain concepts to others, you deepen your own understanding.
Key Takeaway
Improving your coding skills is not about working harder — it is about working with intention. Build things. Read great code. Test relentlessly. Learn your tools. Engage with other developers. The developers who grow fastest are the ones who consistently practice outside their comfort zone and reflect on what they learn.
MySQL Full-Text Search
A full-text index in MySQL is an index of type FULLTEXT. Full-text indexes can be used only with InnoDB or MyISAM tables, and can be created only for CHAR , VARCHAR , or TEXT columns. MySQL provides a built-in full-text ngram parser that supports Chinese, Japanese, and Korean (CJK), and an installable MeCab full-text parser plugin for Japanese. A FULLTEXT index definition can be given in the CREATE TABLE statement when a table is created, or added later using ALTER TABLE or CREATE INDEX . For large data sets, it is much faster to load your data into a table that has no FULLTEXT index and then create the index after that, than to load data into a table that has an existing FULLTEXT index.
3 types of full-text searches
- A natural language search interprets the search string as a phrase in natural human language (a phrase in free text). Full-text searches are natural language searches if the
IN NATURAL LANGUAGE MODEmodifier is given or if no modifier is given. - A boolean search interprets the search string using the rules of a special query language. The string contains the words to search for. It can also contain operators that specify requirements such that a word must be present or absent in matching rows, or that it should be weighted higher or lower than usual. Certain common words (stopwords) are omitted from the search index and do not match if present in the search string. The
IN BOOLEAN MODEmodifier specifies a boolean search. - A query expansion search is a modification of a natural language search. The search string is used to perform a natural language search. Then words from the most relevant rows returned by the search are added to the search string and the search is done again. The query returns the rows from the second search. The
IN NATURAL LANGUAGE MODE WITH QUERY EXPANSIONorWITH QUERY EXPANSIONmodifier specifies a query expansion search.
Create full-text indexes
// Add FULLTEXT KEY on table creation CREATE TABLE user ( id INT NOT NULL AUTO_INCREMENT, first_name varchar(255) DEFAULT NULL, last_name varchar(255) DEFAULT NULL, email varchar(255) DEFAULT NULL, PRIMARY KEY (id), FULLTEXT KEY (first_name,last_name,email) );
ALTER TABLE user ADD FULLTEXT(first_name,last_name,email);
Note that once you full-text index a table, you have to specify all full-text indexed columns of that table on your query.
SELECT * FROM user
WHERE MATCH (first_name,last_name,email)
AGAINST ('folau' WITH QUERY EXPANSION);
It’s important to know that while this is working. It is not a “go to” as for a production searching functionality. Elasticsearch or other search engines are better for that. I would use mysql full-text for a small application but as that small application grows, I would move searching to a search engine like Elasticsearch.
Java Interview – String
1. What is String in Java?
String is a Class in java and defined in java.lang package. It’s not a primitive data type like int and long. String class represents character Strings. String is used in almost all the Java applications and there are some interesting facts we should know about String. String in immutable and final in Java and JVM uses String Pool to store all the String objects.
Some other interesting things about String is the way we can instantiate a String object using double quotes and overloading of “+” operator for concatenation.
2. Difference between String, StringBuilder, and StringBuffer?
The string is immutable and final in Java, so whenever we do String manipulation, it creates a new String. String manipulations are resource consuming, so java provides two utility classes for String manipulations – StringBuffer and StringBuilder.
StringBuffer and StringBuilder are mutable classes. StringBuffer operations are thread-safe and synchronized where StringBuilder operations are not thread-safe. So in a multi-threaded environment, we should use StringBuffer but in the single-threaded environment, we should use StringBuilder.
StringBuilder performance is fast than StringBuffer because of no overhead of synchronization.
3. Why is String immutable or final?
There are several benefits of String because it’s immutable and final.
- String Pool is possible because String is immutable in java.
- It increases security because any hacker can’t change its value and it’s used for storing sensitive information such as database username, password etc.
- Since String is immutable, it’s safe to use in multi-threading and we don’t need any synchronization.
- Strings are used in java classloader and immutability provides security that correct class is getting loaded by Classloader.
4. What is a String pool?
As the name suggests, String Pool is a pool of Strings stored in Java heap memory. We know that String is a special class in Java and we can create String objects using the new operator as well as providing values in double-quotes.
Check this post for more details about String Pool.
5. How to reverse a String?
public static void main(String[] args)
{
System.out.println("Enter string to reverse:");
Scanner read = new Scanner(System.in);
String str = read.nextLine();
StringBuilder sb = new StringBuilder();
for(int i = str.length() - 1; i >= 0; i--)
{
sb.append(str.charAt(i));
}
System.out.println("Reversed string is:");
System.out.println(sb.toString());
}
Use StringBuilder reverse() method.
public static void main(String[] args)
{
System.out.println("Enter string to reverse:");
Scanner read = new Scanner(System.in);
String str = read.nextLine();
StringBuilder sb = new StringBuilder(str);
System.out.println("Reversed string is:");
System.out.println(sb.reverse().toString());
}
6. Why String is a popular HashMap key?
Since String is immutable, its hashcode is cached at the time of creation and it doesn’t need to be calculated again. This makes it a great candidate for the key in a Map and it’s processing is fast than other HashMap key objects. This is why String is mostly used Object as HashMap keys.
7. What are the different ways to create a string?
String str = new String("folau");// by using the new keyword
String str1 = "folau";// by using the double quotes
8. Check for palindrome (string is equal to its reversed version)
private static boolean isPalindromeString(String str) {
if (str == null)
return false;
int length = str.length();
System.out.println(length / 2);
for (int i = 0; i < length / 2; i++) {
if (str.charAt(i) != str.charAt(length - i - 1))
return false;
}
return true;
}
Use StringBuilder reverse() method.
private static boolean isPalindrome(String str) {
if (str == null)
return false;
StringBuilder strBuilder = new StringBuilder(str);
strBuilder.reverse();
return strBuilder.toString().equals(str);
}
9. Remove a single character from a string
Use the Character class to create a string and pass it to the replaceAll method.
private static String removeChar(String str, char c) {
if (str == null)
return null;
return str.replaceAll(Character.toString(c), "");
}
10. Convert String to char and vice versa?
We can’t convert a string to a char because a char is a single character. On the other hand, we can use charAt or toCharArray to convert chars to a string.
11. Find all permutations of a string
public static Set<String> permutationFinder(String str) {
Set<String> perm = new HashSet<String>();
//Handling error scenarios
if (str == null) {
return null;
} else if (str.length() == 0) {
perm.add("");
return perm;
}
char initial = str.charAt(0); // first character
String rem = str.substring(1); // Full string without first character
Set<String> words = permutationFinder(rem);
for (String strNew : words) {
for (int i = 0;i<=strNew.length();i++){
perm.add(charInsert(strNew, initial, i));
}
}
return perm;
}
public static String charInsert(String str, char c, int j) {
String begin = str.substring(0, j);
String end = str.substring(j);
return begin + c + end;
}
public static void main(String[] args) {
String s = "AAC";
String s1 = "ABC";
String s2 = "ABCD";
System.out.println("\nPermutations for " + s + " are: \n" + permutationFinder(s));
System.out.println("\nPermutations for " + s1 + " are: \n" + permutationFinder(s1));
System.out.println("\nPermutations for " + s2 + " are: \n" + permutationFinder(s2));
}
11. Find the longest palindrome in a string.
public static void main(String[] args) {
System.out.println(longestPalindromeString("1234"));
System.out.println(longestPalindromeString("12321"));
System.out.println(longestPalindromeString("9912321456"));
System.out.println(longestPalindromeString("9912333321456"));
System.out.println(longestPalindromeString("12145445499"));
System.out.println(longestPalindromeString("1223213"));
System.out.println(longestPalindromeString("abb"));
}
static public String intermediatePalindrome(String s, int left, int right) {
if (left > right) return null;
while (left >= 0 && right < s.length()
&& s.charAt(left) == s.charAt(right)) {
left--;
right++;
}
return s.substring(left + 1, right);
}
// O(n^2)
public static String longestPalindromeString(String s) {
if (s == null) return null;
String longest = s.substring(0, 1);
for (int i = 0; i < s.length() - 1; i++) {
//odd cases like 121
String palindrome = intermediatePalindrome(s, i, i);
if (palindrome.length() > longest.length()) {
longest = palindrome;
}
//even cases like 1221
palindrome = intermediatePalindrome(s, i, i + 1);
if (palindrome.length() > longest.length()) {
longest = palindrome;
}
}
return longest;
}
12. Why char array is preferred over string for database password?
String is immutable in Java and stored in String pool. Once it’s created it stays in the pool until unless garbage collected, so even though we are done with password it’s available in memory for longer duration and there is no way to avoid it. It’s a security risk because anyone having access to memory dump can find the password as clear text.
If we use a char array to store password, we can set it to blank once we are done with it. So we can control for how long it’s available in memory that avoids the security threat with String.
13. Check if two strings are the same?
String s1 = "abc";
String s2 = "abc";
String s3= new String("abc");
System.out.println("s1 == s2 ? "+(s1==s2)); //true
System.out.println("s1 == s3 ? "+(s1==s3)); //false
System.out.println("s1 equals s3 ? "+(s1.equals(s3))); //true
There are two ways to check if two Strings are equal or not – using “==” operator or using equals method. When we use “==” operator, it checks for the value of String as well as the reference but in our programming, most of the time we are checking equality of String for value only. So we should use the equals method to check if two Strings are equal or not.
There is another function equalsIgnoreCase that we can use to ignore case.
13. is String thread-safe?
Strings are immutable, so we can’t change its value in runtime. Hence it’s thread-safe and can be safely used in a multi-threaded environment.
December 16, 2019Share ideas and findings
Software development is a team sport. The best engineers are not just skilled coders — they are effective communicators who multiply their team’s output by sharing knowledge. If your ideas live only in your head, they die the moment you leave the project. Sharing ideas and findings is how teams build resilient, maintainable software.
Code Reviews: Give and Receive Feedback Well
Code reviews are the most consistent form of knowledge sharing on any team. A good review is not about proving someone wrong — it is about making the codebase better together.
When reviewing:
- Focus on logic, readability, and maintainability — not style preferences.
- Ask questions instead of making demands: “Could we simplify this?” instead of “This is wrong.”
- Point out what is done well, not just what needs fixing.
When receiving feedback:
- Do not take it personally. The review is about the code, not you.
- If you disagree, explain your reasoning — then be willing to compromise.
Here is an example of a Java method that a reviewer might flag:
// Before: reviewer flags this — too many responsibilities public void process(Listorders) { for (Order o : orders) { if (o.getStatus() == null) continue; if (o.getTotal() > 1000) { emailService.sendHighValueAlert(o); } o.setProcessedDate(LocalDate.now()); orderRepository.save(o); } } // After: refactored based on review feedback public void processOrders(List orders) { List validOrders = filterValid(orders); validOrders.forEach(this::flagHighValueOrders); validOrders.forEach(this::markAsProcessed); orderRepository.saveAll(validOrders); } private List filterValid(List orders) { return orders.stream() .filter(o -> o.getStatus() != null) .collect(Collectors.toList()); } private void flagHighValueOrders(Order order) { if (order.getTotal() > HIGH_VALUE_THRESHOLD) { emailService.sendHighValueAlert(order); } } private void markAsProcessed(Order order) { order.setProcessedDate(LocalDate.now()); }
The reviewer’s comment might be: “This method is doing filtering, alerting, and persistence in one loop. Can we break it into smaller methods so each has a single responsibility?” That kind of feedback teaches the whole team, not just the author.
Pair Programming: When It Pays Off
Pair programming is not about having two people do one person’s job. It is a targeted tool for specific situations:
- Onboarding new team members — nothing transfers context faster than coding together.
- Complex or risky changes — two sets of eyes catch subtle bugs in real time.
- Debugging production issues — one person drives while the other researches logs and documentation.
You do not need to pair all day. Even 30 to 60 minutes on a tough problem can save hours of back-and-forth in code review later.
Knowledge Sharing: Make It a Habit
Great teams build systems for sharing knowledge, not just relying on hallway conversations.
- Team wikis — Document how your services work, common troubleshooting steps, and environment setup guides. Use Confluence, Notion, or even a GitHub wiki.
- Architecture Decision Records (ADRs) — When the team makes a significant technical decision, write it down. Future engineers will thank you for explaining why you chose PostgreSQL over MongoDB, not just that you did.
- Tech talks and brown bags — A 15-minute demo of a new library or pattern you discovered is one of the highest-leverage activities a senior developer can do.
In Python, a simple ADR might live right in your repo:
# docs/adr/002_use_celery_for_background_tasks.py
"""
Architecture Decision Record: Use Celery for Background Tasks
Status: Accepted
Date: 2025-06-15
Context:
Our API endpoints for report generation are timing out
because PDF creation takes 30-60 seconds.
Decision:
Use Celery with Redis as broker for async task processing.
Consequences:
- API responses return immediately with a task ID
- Clients poll a status endpoint for completion
- Team must learn Celery basics (see wiki: /docs/celery-guide)
- Redis becomes a new infrastructure dependency
"""
Documentation as Communication
Every commit message and pull request description is a form of communication with your future team — including future you.
Commit messages should explain why, not what. The diff already shows what changed.
# Bad fix bug # Good Fix null pointer in OrderService when guest users checkout Guest users have no saved address, causing getDefaultAddress() to return null. Added a fallback to prompt for manual entry. Fixes #1042
Pull request descriptions should give reviewers the context they need to review effectively. Here is an example of a well-structured PR description:
## Summary Refactor payment processing to support multiple payment providers (Stripe, PayPal) instead of the current Stripe-only implementation. ## Motivation Product team confirmed we are launching PayPal support in Q3. Current code has Stripe logic hardcoded throughout OrderService. ## Changes - Introduced PaymentProvider interface - Moved Stripe logic into StripePaymentProvider - Added PayPalPaymentProvider (behind feature flag) - Updated OrderService to use provider abstraction ## Testing - Unit tests for both providers - Integration test with Stripe sandbox - PayPal tested manually in dev environment ## Rollback Plan Disable PayPal feature flag. Stripe path is unchanged.
Tools That Enable Sharing
- Slack or Teams channels — Create dedicated channels like #tech-discussions or #til (today-I-learned) where engineers post discoveries.
- Confluence or Notion — Centralized documentation for runbooks, onboarding guides, and architecture overviews.
- GitHub Discussions or Pull Request comments — Keep technical conversations close to the code so they are discoverable later.
The goal is to reduce the “bus factor” — the number of people who can get hit by a bus before the project stalls. If only one person understands a critical system, that is a risk to the entire team.
Senior Tip
The best code is code your team understands, not just code that works. Writing clever, compact code that only you can read does not make you a 10x engineer — it makes you a bottleneck. Write code that a new team member can pick up in their first week. Share your reasoning in reviews, document your decisions, and invest in your team’s collective understanding. That is what separates senior engineers from those who simply have senior titles.
December 2, 2019