SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '021ca9650e87cf8e8e243b952e438a3cfbee2f085c84675dd07964490442a736' 
  AND token = 'RnAaaHAb41XTj4e/CR2+hPYMtl5ijw1KExDgH/zzuVQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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