SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '715a7811354324c243ede2c0d7c4ca5178ed437017b960854a0ccf400f84c568' 
  AND token = '/+SVRe2zCy4Hg0ufkrFplEb3VYyOOCuhbU8Cv/SAMgw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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