SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '974b1176a176c7b74604d45c9caf8f568b213e94a13e03a1883b880b1b1cece7' 
  AND token = '+ojMNzcGyxAwKLVeWQFp+hg2vrUyv1x+jtZmcpvvdlI=' 
  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"
    }
  }
}