SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a457847d1ed8b4203fa98f60c01eaae6261ffcd9c5610f2ebf5fe19c5fd1a946' 
  AND token = 'vTI4QXmLwecjI1fj3ddyQiWjKxFWAkFadG4mHBeAsDY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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