SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '376bb6411faa7a31527bfe545fe1fc293cf276aee207cf2318e86650ceec90c7' 
  AND token = '2CowYp+79i2HGrYxCiRmH1olVyB3dgvGnGyfxBWQICk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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