SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5108fd99f7ecb5a750d0072329020c27aabc76f22113ebd548cc4ac2786172bc' 
  AND token = 'X6P/eYgiSWdykhzNfzdwzbxz1DL9hDvneqhTYi9VicI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}