SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4db65ce4631d12faa86338c3274547953d99f1e442bde77e3de0e207853da6dc' 
  AND token = 'u0yncawJhAztUSLnhBhlfA8trR+yLNsNEOUjxx3+3rI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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