SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af628e1ccce9b45da181d5cdcd5d46857603b80e9c631841270c1d084030a335' 
  AND token = 'I1NLitfudVkfxJuUwHHmuE0lvwAx27yTCmmZKHvJIxM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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