SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75bb715b2bec2a47410de6e5c94e88a83b9c35e1d9008daa904f5279049f638b' 
  AND token = 'mGoL/iSvMwG5Vr7B2bxSOsAkiXqGmbrhmAzjquZWtV4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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