SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2450acf171af77a1ece846a898db6307e716ff448d2e00361dcd49d8e105af32' 
  AND token = 'poEynQmQWy/BwL9wbP2CtirGaPX5eaBYYmP0yg05/0A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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