SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52984a07029f36115940494672e159c81fb2faa3b06935c4afca70f5343bde4d' 
  AND token = 'z8ua1dPDgiT438O72ncT2RxpYzTZHxZUqOOlDH2mrZg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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