SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a3045128f6be0487eddc47cda6ae5d2af0246cc5d4366d3b9f0e35314139779' 
  AND token = '1QBrB1JVnagmBsWc8VQXT6+FcmzRgwuvaw0VjYzMYu0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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