SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '375ca840b41925dca17e0f40693d837750a455559e8b9ff60af0b92f15e15782' 
  AND token = 'Fn/VI5hIYDWoubyI5phtzlzp+NZkXpFKu4A+wI+mNtU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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