SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf3ef9bee8e453f359bc0e7ed14366f29b71a003d23c4b48f5311283f619db37' 
  AND token = 'qQz3/pFqstOtoOmXYJ5bHVM2XMBrenCaHAYRC1v+ZIQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}