SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4f821f0e5c76683129f89636f0fc0afc27e0cd556a991bbdb160f66f33856b42' 
  AND token = '6ycpyX6INiG0DCYc49fwjj9FuHau71UvkykzR9Xw0IM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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