SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3d26489cb87ad7a80fc1d2d0dea013688bec06354aa6fac0dfc1f341194fe55' 
  AND token = 'fklyIM+TgzfRkfIIJDR8B/c11ceCTw2sFdtmQQ1P5Zs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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