SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6bf9b1ea994d3247dabdd764f595f9633b0d2876b5234a224c297edd285d657' 
  AND token = 'VKROmzvveNItlN3loDfOGxDbypsmA37liwiLipR4NmM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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