SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '509e0a4e74cc004882fbeba7a608aac65fd10cc8e332de9cd7377b6c51e1516d' 
  AND token = 'u3vQbLudZbpxQLekSt7rGkMvCfVigmRlaXvVIco9lWQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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