SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a0021b51d67787062ed36de7a4b8773042933d74bdae2a07b7071412e9c3294f' 
  AND token = 'oNAprTBdP+guQHhPoNVWRu5SlqtrtixxSgZQZh+ggT8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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