SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '73797655cfbbadf57ee015bccadf8d164d1c1f737e152f337555cbf42a4c2d4e' 
  AND token = 'isI/s7MWPzuj1CUQJQFmv0+77PkCf26SrAGTNfKkWBk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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