SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '87913b81983ce065fc19e7425eaf20de79fedb83065d2fe5b9594498460a03eb' 
  AND token = 'PQmJAir7+8Ua150rzoj7zhJX8JgmmRm/ng2AoD0ZHCY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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