SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c39ed5a53e74afdaea47164fa80e20d0d6d2cd903e521ea3c9cd5545f5a6b730' 
  AND token = 'VkOnJzhdyMWwX1hyh3ixYUDz1V4k3EZOWP+CawoxeKw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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