SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '39f99ac0cffe903f8e1193c7b4047d23543f6aa68dd6f833880dc746fa96c20d' 
  AND token = '8MXqMGeowAJYLj5OKOH+vn9yFH0Px1dGv28oO+GfjUQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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