SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52ff69b9f6b7319aa13e55260527acc7921eebaf4e3bdf0e08cdccfc8144ac97' 
  AND token = 'SwhDLjNXJ+KOrC+1K7OkDMzIBPPc7ekpAWdfzM32VTM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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