SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd982a9d272458066ce913034f5e38e971a56c17ac3b35dc18652bcf607390a3c' 
  AND token = '4unQR7cBAGZuLtarkvzPjQqqbiY64mtaGqgAgswizcc=' 
  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"
    }
  }
}