SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fef83eae83eb185abe8d42c220a0323d048213df4a4e16ca3735a7c27e958792' 
  AND token = 'xo+/NqzfCjjMuuQdTDPZMhbaMk7r7142eEevNImlV4E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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