SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '19c6a54f596cc5e50610b531463f1baf2544f908b3655e80dfb352e066579c1f' 
  AND token = 'Psz6xHSp+vghAClvJhTmdW45q+rnhvupIOEHQgcjxw4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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