SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d76144d3d481a62c0be69d97ef526f355f514a934d5934d77eea46a3528a921' 
  AND token = 'KXSBteRiG7vuCncM1OF/jiKOKmapeRZcLk1/yUwhSLg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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