SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc67e697b3bcccd285c931cb4a23d8d843da01656108488f212799a658d4ac5a' 
  AND token = 'CWjbJjmbFf4sleREsod+UbBcvPxZKfyVDQwYOGidhyU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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