📂 Databases & Backend Theory

71. What is the difference between SQL and NoSQL?
72. What is ACID and where is it important?
73. What is normalization and denormalization?
74. What is indexing and when is it useful?
75. What is sharding vs replication?
76. What is the difference between strong and eventual consistency?
77. What is a transaction and when do you roll it back?
78. What is connection pooling?
79. What is the CAP theorem?
80. How do you design a scalable schema for user‑generated content?

💡 Coding & Problem‑Pattern Practice

81. Write a function to find the sum of all elements in an array.
82. Write a function to reverse a string.
83. Write a function to find the longest palindromic substring.
84. Write a function to implement debounce.
85. Write a function to implement throttle.
86. Write a function to flatten a nested array.
87. Write a function to implement a simple pub/sub pattern.
88. Write a function to implement basic Promise.all.
89. Write a function to group anagrams.
90. Write a function to implement a simple LRU cache.

🧠 Behavioral & System‑Design (Full‑Stack / SWE)

91. Walk me through a project you built end‑to‑end.
92. Describe a time you exceeded performance / scalability requirements.
93. Tell me about a time you debugged a production bug.
94. Tell me about a time you reduced technical debt in a codebase.
95. How do you design a simple chat / notification system?
96. How would you design a file‑uploading service?
97. How would you design a task‑management / kanban app?
98. How do you collaborate between frontend and backend teams?
99. How do you handle conflicting requirements from product and infra?
100. How do you prepare yourself for system‑design interviews?

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