SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '793f0f3d8341f670f818a674b1f75b6b9ea6ccfb32ee8f2b6cc8b45da108ae21' 
  AND token = '1ouFLazo+045unTRYsDtwubZZvCFmXFBCaE8BwQaKvg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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