SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef8e339519f4b7e2fa0b7204ed02c718a47093bd244b14a893c257acba5da58f' 
  AND token = 'zTPXHVxmFlfcU+QjVOjLRE3mU6z8BDOGG/zaeucxe3M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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