SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a273511a4222c56d780929f20d27e8485a3496bf155259e01e749532bef20876' 
  AND token = 'MTLwxL+0eD7CPUT+OXGpa2bf25CKcyN1QCwgmnbtduQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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