SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a8693a19457d0da210ba94586cde101c4f7bba403c54108b0f44597c5a659126' 
  AND token = 'CHWHkrg+wuF5dbOD1luG+2sfcyIBHRZmCpkqIUMJpXw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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