Node.js Practical — Redis caching — Variable/Import Error

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Node.js Practical Debugging — Redis caching (Variable/Import Error). A developer says the project suddenly stops with an error such as ReferenceError, TypeError or MODULE_NOT_FOUND. Find the root cause and show the corrected code. The specific area is stale data, key mismatch and JSON serialization. Assume a real Express/Node.js project where the developer needs a reliable, maintainable fix. Explain why the buggy version can fail, then provide corrected code and the expected behavior. Do not hide the root cause behind a generic 'restart the server' answer. BUGGY/PROBLEM CODE: const client = createClient({ url: process.env.REDIS_URL }); await client.connect(); await client.set('user:1', {name:'Manish'}); TASK: Find the exact problem and write the production-safe correction.
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Answer & Explanation

4 Answers
Verified

Possible but Incorrect Code

const client = createClient({ url: process.env.REDIS_URL }); client.on('error', err => console.error('Redis error:', err)); client.connect(); await client.set('user:1', JSON.stringify({name:'Manish'}), { EX: 300 }); const raw = await client.get('user:1'); const user = raw ? JSON.parse(raw) : null;
Additional Explanation
यह option जानबूझकर एक common bug/unsafe approach दिखाता है। इसे production solution के रूप में इस्तेमाल करने से पहले variable scope, async flow, module path, validation, error handling और security checks verify करें। ऊपर दिए गए correct option से exact difference compare करें.
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Editorial Answer 1
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Possible but Incorrect Code

const client = createClient({ url: process.env.REDIS_URL }); await client.connect(); await client.set('user:1', {name:'Manish'});
Additional Explanation
यह option जानबूझकर एक common bug/unsafe approach दिखाता है। इसे production solution के रूप में इस्तेमाल करने से पहले variable scope, async flow, module path, validation, error handling और security checks verify करें। ऊपर दिए गए correct option से exact difference compare करें.
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Editorial Answer 2
Verified

Possible but Incorrect Code

const client = createClient({ url: process.env.REDIS_URL }); await client.connect(); await client.set('user:1', {name:'Manish'});
Additional Explanation
यह option जानबूझकर एक common bug/unsafe approach दिखाता है। इसे production solution के रूप में इस्तेमाल करने से पहले variable scope, async flow, module path, validation, error handling और security checks verify करें। ऊपर दिए गए correct option से exact difference compare करें.
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Editorial Answer 3
Verified Correct Answer

Correct Code / Solution

const client = createClient({ url: process.env.REDIS_URL }); client.on('error', err => console.error('Redis error:', err)); await client.connect(); await client.set('user:1', JSON.stringify({name:'Manish'}), { EX: 300 }); const raw = await client.get('user:1'); const user = raw ? JSON.parse(raw) : null;
Additional Explanation
Root cause: stale data, key mismatch and JSON serialization. The important debugging step is to verify the exact runtime value, module path, middleware order, environment variable, database/model export, or asynchronous result before changing unrelated code. The corrected version adds explicit validation/error handling where appropriate. Expected behavior: the code should either complete the requested operation or return/log a controlled error instead of failing silently, returning undefined unexpectedly, or crashing the process.
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Editorial Answer 4