SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b21192de38c9ff365e03043128520156a3e49f43bd5500a5c14ca482a7891fa' 
  AND token = 'ykj4dZVIZupkTHp9RwUpfHUNjUlsA/QvUyqS6LHxjyA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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