SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ee2398ec44733005bdbed414e1704776ba1f70e8c76105234c4f873a8a9222c' 
  AND token = '8ShzlBEmSeo+coRTY19saYDf5QEtK8B87vMxU1lcMtc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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