SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c488bd7a5498d6c1a2d31e57b55921dbe3eacdab4d1549282911f3f478e8bdab' 
  AND token = 'I3zVVrMvCHdEgUTXWBPYKN5GZjH7eoKlwHjqxTNWzZ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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