SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '947eb2b8dda88dabe18336a5b3ce164499f51f39608a0f558192195974a3b50f' 
  AND token = '6w+WrRTPeauwV8qr+ljuSd0+qSxwPQzmtNTjrB1JZzA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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