# Debasis Das

> Founding Engineer at Retell AI | Ex-Twilio

Location: San Carlos, California, United States
Profile: https://flows.cv/debasis

Software Developer | Distributed Systems | Real-Time Communication | Conversational AI Enthusiast

With over 15 years of experience building scalable distributed systems, I specialize in VoIP (SIP) applications, resilient REST APIs and cloud-native architectures on AWS. I thrive on designing fault-tolerant systems that deliver real-time communication at scale. Recently, I’ve ventured into Conversational AI, intrigued by its potential to transform human-computer interaction. I'm excited to connect with visionary builders and disruptors pushing the boundaries of what software can do.

## Work Experience
### Founding Engineer @ Retell AI
Jan 2025 – Present
Building the best Voice AI platform.

### Senior Software Engineer @ Twilio Inc.
Jan 2016 – Jan 2025 | San Francisco
- Contributed to the design and development of Twilio’s Voice Conversational AI capabilities.
- Contributed to building and scaling a high-performance service responsible for orchestrating the ConversationalAI flow between Twilio’s internal TTS/ASR/STT endpoints, customer's servers and Twilio’s media engine.
- Building a solution for customers to own and manage their Mobile Push Notification bindings instead of relying on Twilio managed bindings. This feature will provide flexibility to customers using Twilio Voice SDKs who rely on APN/FCM VoIP Push Notifications for call management.
- Built an in-band channel to transfer and receive custom events/messages to and from Twilio Voice Mobile and JS SDKs.
- Built the integration of Voice Channel into Twilio Frontline(TM) product. Extended persistent storage to work seamlessly with Mysql and in-house datastore(GraphQL+Cockroach-backed).
- Build, maintain, deploy and continuously improve the voice core of Twilio which includes the products Twilio Sip Trunking, Twilio Clients(WebRTC and Mobile) and the Twilio Programmable Voice around the globe.
- Lead multiple projects with contributions at various levels, from architectural decisions to implementation, deployment and bug fixes.
- Built the Twilio Sip Trunking product from scratch, which comprises of various micro services including Sip Applications and REST services that perform various functions ranging from core routing to billing.
- Built a REST service to authenticate JWT tokens used by Twilio Voice SDKs.
- Built a SIP Application called ‘Play’ which aims at guiding new Twilio users to self verify their newly setup infrastructure.
- Developed a SIP application using Mobicents Sip Servlets(JSR-289), which tests & monitors Twilio’s SIP cluster end-to-end, round the clock.
- Lead a small team to implement interworking between Twilio's Programmable Voice core and VoIP E911 termination provider.

### Software Engineer II @ Twilio Inc.
Jan 2013 – Jan 2016 | San Francisco Bay Area
- Building micro services in the AWS cloud.
- Develop and maintain scalable SIP applications in Java. 
- Develop Dropwizard(Java) based distributed and scalable REST services.
- Work with third party persistent storage as Amazon DynamoDB.
- Consume and publish to Kafka Topics.
- Develop a JSR289 based Sip Application using Java and Python(as test scripting) for End-to-End Testing of Twilio's SIP/Telephony core.
- Write CHEF scripts for provisioning and managing AWS instances.
- Write Unit Tests in SipUnit/JUnit.

### Senior Software Engineer @ Movik Networks
Jan 2011 – Jan 2013
Responsibilities include:
1. Create in automation framework(Python 2.x) for S1AP & GTPv2 LTE protocol modules of Movik solution.
2. Develop protocol conformance framework for LTE specifications for Movik solution.
3. Provide UMTS & LTE protocols consultation to engineering groups in Movik.

### Senior Software Engineer @ Sycamore Networks
Jan 2010 – Jan 2011
1. Provide UMTS(RRC-RLC-MAC/NBAP/RANAP) protocol consultaion to Sycamore Networks.
2. Develop IXIA based scripts for UMTS protocol conformance of Sycamore Networks solution.
3. Design scenario based tailor-made custom scripts for Sycamore IQStream control plane. eg: Common Transport Channel Setup procedure.
4. Design End-End call-flows from specs & develop test scripts involving scenarios like HO with ASU, Cell_Update, PDP Context Activation, CTCH Setup, PDP Context Modification, Sec-PDP, RadioBearer Setup/Reconfig, RL Sync, RAB Assignment procedures etc. for system Testing of Sycamore Solution.
5. L2/L3 switching with Netgear & Cisco switches.

### Senior Software Engineer Team Lead @ Larsen & Toubro Infotech Ltd.
Jan 2008 – Jan 2011 | Greater Boston Area
Responsibilities across various projects in L&T include but not limited to:

At Sycamore Networks,Chelmsford MA:
1. Provide UMTS(RRC-RLC-MAC/NBAP/RANAP) protocol consultation to Sycamore Networks.
2. Develop IXIA based scripts for protocol conformance of Sycamore Networks solution.
3. Design scenario based tailor-made custom scripts for Sycamore solution's control plane e.g: Common Transport Channel Setup procedure.

At Motorola Inc.,San Diego CA:
1. Manage a team of 6 ICs at Motorola.
2. Resource-planning, Task-scheduling & reporting as a TeamLead.
3. Deliver OMA-DM solution to Boost service provider.

At Samsung Electronics:
1. Develop TTCN-3 framework for S1AP & GTPv2 stack on eNodeB & MME.
2. Build a LTE standards competence team.

At Alvarion Ltd.,Tel Aviv, Israel:
1. Provide 802.16e(WiMAX) consulting to Alvarion.
2. Protocol Testing of WiMAX MAC layer of Alvarion base station & CPE.
3. IOT of Alvarion BS with Sequans stack vendor & IOT with different CPE vendors.

### Senior Wireless Engineer/Team Lead @ Motorola Solutions
Jan 2009 – Jan 2010 | San Diego, California, United States
1. Managed a team of 6 ICs at Motorola.
2. Resource-planning, Task-scheduling & reporting as a Team Lead.
3. Delivered OMA-DM solution to Boost wireless service provider.

### Senior Wireless Engineer @ Alvarion Technologies
Jan 2008 – Jan 2009 | Tel Aviv, Israel
System integration of Alvarion WiMAX module and 802.16e(WiMAX) consultant to Alvarion.

### Senior Engineer. @ Tata Elxsi
Jan 2007 – Jan 2008
System integration of WiMAX MAC layer & development of automation layer using TCL and Perl.


## Education
### B.E. in Computer Science & Engg, Communication.
Anna University Chennai

### 10th Grade in PCM-B
Sainik School BBSR


## Contact & Social
- LinkedIn: https://linkedin.com/in/debzdas
- Portfolio: http://www.movik.net
- Portfolio: http://www.sycamorenet.com
- Portfolio: http://www.lntinfotech.com

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Source: https://flows.cv/debasis
JSON Resume: https://flows.cv/debasis/resume.json
Last updated: 2026-04-10