SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bb25edf8f32e584aee540654c376ab69ead181df8e61f5e2f57d68781335f58c' 
  AND token = 'qRst33JVulD+XJHicz4j9poNRyGIZebQAgPFqFtm6Qo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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