SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51f7fe36bf1528f2d98b832c0b95143406355c27a8206ddd9d4bcd9946263845' 
  AND token = 'kvGvgsSxE9WUsBoqbxUDFRWrl7LMY2BkDMKN5wmQwVY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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