SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3b8043f76a7e96a1a7e0e2bb30f2571704975ac922bf412112f6cce40e393d34' 
  AND token = 'XxSiNNELPoJ8badkLtCFx1bxxPEm2pBBj8WBmEadzNs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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