SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6699fa846c58408ed011561750694c909fcb96fa75d86fead50513a75e278698' 
  AND token = '4BcRhIyTydQ4JU//UWcT4UAt0+oPkzl99/RrRzgJpBo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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