SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56fb28e7a816315bf47aef3d63124487e15a1afc0026f24f16a1e324200e4ef6' 
  AND token = 'fihQKaVJvqSdnMYgp+tMkhTT6EljvEABbcchlNCy6ts=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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