SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6299e69f744e456463470233ffe55471c41360d3dbbacaece8db266c493ba84d' 
  AND token = 'zx+QhW76wcVfCnRgKRvFupCypalKG13tpHfKLwJv5Qg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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