SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42d377c94299bcf17199823336732c263abf87854131ddc05bde54c7cb3f0850' 
  AND token = '6Iq8iCpGwp2lmHMDc7R3EnupiAxVkUYp6cT+JDJjGm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}