SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a28543121e04d292e3aea932ead4dc32e65b81bcf6869313132c314e37860264' 
  AND token = 'sHq+9faGHAVGLSC/Dvwpf0+B/bFmJe4UTul+AWXmZNo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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