SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81fe3c78142685c730b6b309c017bb9f6ca84897a68b50dfcee35d90eb5f1c05' 
  AND token = 'K3gpA2AyTAgcq7if34r8eJMyslXcWSOTZ2Om4UPSn4M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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