SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd30b5a59729166ddb2a375d4c11215574c38889e9cc31400dd9d2574463b4b7a' 
  AND token = '6AU4vfTJZjhoMvtulNG2QV6UoqgtKgZuBaXDvW/x1YE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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