SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79376812bfa5e8c4799ebb56266d872f655bfb6398a10fbb9c5e6b772c91d859' 
  AND token = '3xlY4mHhNLnqA6oB7LyZhPKv10yku9EXDkk0X/bBhSw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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