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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42e9351166a37e5afca9a564ba7e6b0aa54e6c6d73623d2d071386c9aa46aea3' 
  AND token = '91cDAq4IW+0IPa0UO/nttZ3PXXOIM0rTdGR7XSdUw+4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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