SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b8e5876a2f2b47e2cabbd00971190facb57f7d34487a245558f5f009ab1c9f2' 
  AND token = 'Ib6HnEKnbxwZhUsteuBUB/AZaTrojsmvqG8lwGfFDj4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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