SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad9cb9b874f904ac507a16e512850ce4561c496361c2081446be4499e98ddf91' 
  AND token = 'tZkx09VtG77OQJF1bDxCgyNDET70poTGAj7jYp47S1o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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