SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50fe4ddad5b72019de93ec312a6635b50a1608d9c42374b7dd142525f58be0a0' 
  AND token = 'rel81YeyUUjvFEtUo1bxonv0i9r7fjfetApJmaYrFIU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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