SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '74ab19f2746054eb031dc553ea65cd43253f5a6846ddd8aa93cb0d988e4ec97f' 
  AND token = 'AvbbES6j3BFxCGywCB8Sjr+WAYNCYiV2beCOvi+iqyM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}