PhonePe Redis Interview Questions 2026
Published July 22, 2026 · Updated July 22, 2026
5 real Redis interview questions asked at PhonePe. Upvoted by engineers who cleared the loop. Covers System Design, Technical rounds.
5 questions
210 engineers asked
282 upvotes
Company: PhonePe
Technology: Redis
All Redis Questions Asked at PhonePe
PhonePe
Hard
System Design round
KafkaDistributed SystemsPostgreSQL
Design PhonePe's UPI transaction system to handle 1 billion transactions per day.
Cover: request routing to the correct bank, NPCI integration, handling duplicate transactions, consistency vs availability trade-offs, and how you build a reliable audit trail for regulatory compliance.
↑ 89 upvotes · 89 engineers asked this · SDE2
PhonePe
Hard
System Design round
Distributed SystemsKafkaRedis
Design PhonePe's switch - the internal routing layer that forwards UPI requests to the correct bank. It must be highly available (99.999%), handle 50k TPS, and complete each request within 30 seconds (NPCI timeout). Cover: circuit breakers, retries, and bank-specific timeouts.
↑ 66 upvotes · 43 engineers asked this · SDE2
PhonePe
Hard
Technical round
PostgreSQLRedisJava
Explain how PhonePe handles transaction deduplication. A user taps "Pay" twice due to network lag. The same debit must not happen twice. Walk through idempotency at the API level, database level, and bank integration level.
↑ 55 upvotes · 35 engineers asked this · SDE2
PhonePe
Hard
System Design round
KafkaPostgreSQLRedis
Design PhonePe's merchant settlement system. Thousands of merchants receive daily settlements of their collected payments minus fees. How do you compute net payables, batch into bank transfers, and provide a reconciliation report?
↑ 54 upvotes · 33 engineers asked this · SDE2
PhonePe
Medium
Technical round
2-5 yearsRedis
You use Redis to cache OTPs with a 5-minute TTL. How does Redis actually expire keys internally — does it scan the whole keyspace on a timer?
↑ 18 upvotes · 10 engineers asked this · SDE2
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Frequently asked questions
Design PhonePe's UPI transaction system to handle 1 billion transactions per day.
Design PhonePe's UPI transaction system to handle 1 billion transactions per day.
Cover: request routing to the correct bank, NPCI integration, handling duplicate transactions, consistency vs availability trade-offs, and how you build a reliable audit trail for regulatory compliance.
Design PhonePe's switch - the internal routing layer that forwards UPI requests to the correct bank. It must be highly available (99.999%), handle 50k TPS, and complete each request within 30 seconds (NPCI timeout). Cover: circuit breakers, retries, and bank-specific timeouts.
Design PhonePe's switch - the internal routing layer that forwards UPI requests to the correct bank. It must be highly available (99.999%), handle 50k TPS, and complete each request within 30 seconds (NPCI timeout). Cover: circuit breakers, retries, and bank-specific timeouts.
Explain how PhonePe handles transaction deduplication. A user taps "Pay" twice due to network lag. The same debit must not happen twice. Walk through idempotency at the API level, database level, and bank integration level.
Explain how PhonePe handles transaction deduplication. A user taps "Pay" twice due to network lag. The same debit must not happen twice. Walk through idempotency at the API level, database level, and bank integration level.
Design PhonePe's merchant settlement system. Thousands of merchants receive daily settlements of their collected payments minus fees. How do you compute net payables, batch into bank transfers, and provide a reconciliation report?
Design PhonePe's merchant settlement system. Thousands of merchants receive daily settlements of their collected payments minus fees. How do you compute net payables, batch into bank transfers, and provide a reconciliation report?
You use Redis to cache OTPs with a 5-minute TTL. How does Redis actually expire keys internally — does it scan the whole keyspace on a timer?
You use Redis to cache OTPs with a 5-minute TTL. How does Redis actually expire keys internally — does it scan the whole keyspace on a timer?