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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '328bc79d753c88323d5747ab9dbabccd008c703b0864a09404905f0a65d1cb8d' 
  AND token = 'yq0QOXu4OOoyriVltCOvMyahoGUmVpoTQy74WM9rldk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}