SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '519191551a7dbdf06452e14cd65d9bb19dd92da23c9167ab674ce77a060eb740' 
  AND token = 'WSG4aBM7fzusVd3h7bV3azJzHg/i64YyfTyzcOgPVUw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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