SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4d55918e375470cfd96f5b73274ee3d87400f20d59843c8239bf697048549b6' 
  AND token = '+kqdg1iwrJ8ZRvKp3zHaU+JakJWPyt9xUX31Aw1x63g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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