SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '031878115026b79ab3f5a598b456c3cfa40bd61dd6d1d743ac9fa6fe2f3bc49a' 
  AND token = 's7V4BXY66km+c3+NB4SsF5yDqMX9vg/HvvFG568693A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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