SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '991b0e072aa00505a1b5a6fc66a03d9b88f0653778865c4a7762819ab5806b32' 
  AND token = '/jVps+zsMgdyJezyrzyDnZKgOjilwyvoOrrN1NIezzY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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