SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f784d12686fff54fd7340729b9bb1e824f708682321a9aade427147f36e4074c' 
  AND token = 'vf/i82ovAENTIG5Zjr5pixpjtaaO939acJZc2cwbi2E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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