SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f63951675cdac874afe8be49597e094282186e0bb26a690fce8d442f53dd5dde' 
  AND token = 'u2rZW726wal3jmBiv4YSrOxzrPY+BEn+UoTMzVzipFo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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