SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3e137262e1e6adf1de4891336492544f77fd165483fd8773b704cdea10f4d2a' 
  AND token = 'fZPhO4pfJsLj9yRYR9//nLIv4VbRZhsweWPyULWWuYc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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