SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '50e301ba4161711caa195192b6ed8e565a79601d8e25b29b151d50abfd4e8f41' 
  AND token = 'TftRPDR/rwzwmF900FnYHKUFAkR1be3YeTlEPbCYqMw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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