SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '437759f9962d137754dbd252b9916508ddb8afddf76efa33bf0824973a7a6743' 
  AND token = 'GmqazoemuBWu2hLlnARY/znyzaTPamGsAHDKPwYrG7g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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