SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18d954abd5c372294fc08b602a6f25e881dbb25a58ae55faa54201f138c480f1' 
  AND token = '9/NdWPlhELCQZR8AhwUFzPuxyQFuo3H8TaE3uvR/CYg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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