SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a248581b3fb6b88bc07cbebed9f425ebd699e75b6ba60489a0e94c96b65a8608' 
  AND token = 'KIEizG7rWoV9X+UTjsG2iBw7+cRzQ/cEmC4LfQEv3uo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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