SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e51d8870aafa63978386b41abcf48c72f9cc1f4a5cd07bf273718fe0022f5cee' 
  AND token = 'DYz+J//WGSmnko+mxj2h4wZk18Y4189j2NAp/mhFJJE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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