Backend Engineer

This is a fully remote position, open to applicants in Mexico, +4 more countries.

📋 Description

• Develop and enhance services that manage real-time call flows, including origination, call control, event delivery, webhooks, rate limiting, blacklists, and metrics.

• Connect the telephony core with the application layer while maintaining low latency, high availability, and predictable behavior under load.

• Create HTTP and WebSocket APIs to orchestrate ongoing calls between the application and the voice core, utilizing OpenAPI contracts and HMAC-SHA256 signed webhooks.

• Collaborate with FreeSWITCH via ESL to implement origination, TRANSFER, BRIDGE, recording, playback, audio streaming, IVR, and DTMF capture.

• Work with event-driven architectures using Kafka, ZeroMQ, Redis, distributed locks, and transactional outbox.

• Implement and evolve rate limits by carrier, blacklists, concurrency control, billing, and operational metrics.

• Develop voice synthesis services by integrating multiple TTS engines, content caching, and low-latency streaming.

• Engage with voicemail detection and voicebots with bidirectional audio.

• Create integrations with LLMs using MCP tools to initiate or terminate calls, play audio, and control streams.

• Develop automated tests and ensure the quality of services in production.

⛳️ Requirements

• 3–6+ years of experience building production backends, with real responsibility for the systems you have developed and operated.

• Strong proficiency in at least one of the following languages and a genuine willingness to work with others: Go, Python (asyncio), or PHP/Laravel.

• Practical experience with concurrency, including async/await, goroutines, queues, workers, and race conditions, with an understanding of why a system degrades under load.

• Experience with event-driven architectures, including brokers or queues in production, idempotency, retries, backpressure, and at-least-once delivery.

• Familiarity with WebSockets and real-time bidirectional communication.

• Proficient in SQL with experience in MySQL 8, including indexing, execution plans, connection limits, and reversible migrations.

• Performance and resilience-oriented mindset, considering p99, failure modes, and behavior under load, not just the happy path.

• Functional technical English for documentation, tools, and basic communication with vendors or support.

• Experience using AI as part of the development process, including code assistants, agents, test generation, or documentation.

• Experience with FreeSWITCH, Asterisk, Kamailio, RTPEngine, SIP, RTP, or WebRTC is a plus.

• Familiarity with Kafka, ZeroMQ, Redis Streams, or other distributed messaging technologies under sustained load is a plus.

• Experience integrating LLMs into real products, including model APIs, agents, RAG, MCP, or automation tools like n8n is a plus.

• Experience with STT/TTS or audio pipelines, including FFmpeg, transcoding, streaming, or PCM normalization is a plus.

• Experience with ClickHouse or other columnar stores for high-volume analytics is a plus.

• Sufficient knowledge of Kubernetes to debug services in production is a plus.

• Experience with React, TypeScript, or Inertia is a plus.

• Familiarity with OpenTelemetry and observability practices is a plus.

🏝️ Benefits

• Competitive salary in USD.

• 100% remote work across all of Latin America.

• Dynamic and collaborative work environment.

• Opportunity to work on real-time voice systems, distributed architectures, and AI applications in production.