SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '88ab16a03515edc0c7c75317b1640f2560d94bf14927d4e0db5c7c50268a83df' 
  AND token = '4/CBTgZQn8jq7M0mRMDBg5xI053hfli9GvidXuONQMY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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