SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'af3c40752f656c3b8285ad51daa64cc8c75805354f1239f9df513c103c802e34' 
  AND token = '2spNtZAIDeuVabJJdhDpPdEGjyKsGunubAY2zwThUzU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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