SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71ab529c301675ed8de229135a6c573e8ac92bb599cafcd7e5534f741f810293' 
  AND token = 'UmGCW9EtKTmBUTNl7Mrvt7wA2MWQSzRUYYj+fFuYjN4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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