SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '517faf222d2f7d7974033a2696318bc6dbbc0b6ca8ca4655ed8bc55c391786a5' 
  AND token = '3j19hY0VSRV56KjCzrakRXJUiafPZCvlVqdtxNXVxO8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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