SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '84c4cb469a50edce9d5ce91bbcb9589f9295f58a9c79380b934fc83e35016409' 
  AND token = 'EG+muXEufEskMcs3pVMRLc4koVBL1ie89a1M7362WBs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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