SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3da8e32caa06acdd21a699378e14148957378f6d2d1f513c62639da7dc226634' 
  AND token = 'yZsOOPu//DO4AZ0zagj9WSMF4MjC//DC679Vkow8VJk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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