SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f833a0a86fe77c849e4e5edb9f1237429c22e5d28f4ec97ba0f9be0be50545b8' 
  AND token = '9Y/vxRZtgLs/LzTJ+OpFrVJ9UJTOh6O+ge/Qkkb+0Pw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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