SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '683aeb4d929194eb1b1d83fa53f62c3041921e6a8bbfc1b7833706df8f4d527f' 
  AND token = '3iZnQWKfMFZGg5mz7n6kgtnC/S2VMK5GP0sj/NOoZbg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00057

JSON explain

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