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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6813df97c2b8f590f550a384435848f2c99e9a83dfbf12a60ef6c9309cd2a51' 
  AND token = 'sMjTtBoFJMNeUkB5oKVFtBT5vl+EjEhddHFzMYbbwRY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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