SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'edd2e7d09d1ee576066705a1f56c93d1912a8cd84e8a543407a1970a5cef90f4' 
  AND token = 'fdNO4MAjYJ5vrTeCDtYnNZ1FDAsRPiqDXYVpHfuksIQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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