SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a2de987bb390fde8a7e78055a61ae8aac3d56764ca20c4004b1e443bf14f81' 
  AND token = 'ICsMB6nTyOjtImU71FyDXpvAW1lD7LovQNBMmcixpJA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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