SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5c703c0f4d42c011aae515575139005f083efca48a3abbbfd4b4273752dcdcf' 
  AND token = 'RRE0FcPC8hU0AMRmFMsRUTZsla4UhqY3N0MuW+hkoV8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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