SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '940c64ee12088a2e56a14539b407293c2d7cede5454c74e9c86ad2ac9cefff53' 
  AND token = 'G+/UNkLjppLXIDXAbBtP+tfPU4VnGZggOmcfdjBJh8Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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