SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4e3952293c00cdb796ff64b5899140396312563a53dc711b323ed43628d8994e' 
  AND token = 'x2/rdVdOJK1KLIotRImbx3AuynkBJBto2FwKMTjVR/A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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