SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4c97f7418f66578a33996a67fbcffbd3f0875029460e773ae05720318bf3b52' 
  AND token = 'BIKzKbz9BXh5fnIyhnciUVWD52RKrvbxjVtrD7kGyl8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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