SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '21f5cc1603026725097ca7520e77f17cd1540b4d53c5386c3a5addf216d77026' 
  AND token = 'bi/vvFXyBwJV5gWQb99E0OMOuM565bx8iaZk20OjwPc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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